Pole Day - Saturday May 15

McLaren M16 cars dominated qualifying during a record-shattering afternoon. The chassis took 1st, 2nd, and 4th starting positions, but the results were not without some surprise. Mark Donohue in the Penske-owned McLaren had broken the 180 mph barrier during practice on Thursday, establishing himself as the favorite for the pole. Donohue lucked out with an early draw on Pole Day, going out third in line. He posted a four-lap average of 177.087 mph to sit on the provisional pole. It was a new track record, but a little disappointing compared to the 180 mph lap he had two days earlier.

Later in the day, Peter Revson, driving a works McLaren, bumped Donohue from the pole with a four-lap average of 178.696 mph.^[13] The pole position far out of reach for the rest of the field. Donohue reportedly suffered handling problems with his car during his run, purportedly as a result of his crew refusing to dial it in as he requested. Donohue then confided with his friend Revson, who then clandestinely borrowed Donohue's chassis set-up advice to knock him off the pole.^[14] Bobby Unser in an Eagle chassis, squeezed between the three McLaren cars by qualifying third.

Second Day - Sunday May 16

Three drivers completed runs, with Bud Tingelstad (170.156 mph) the fastest of the afternoon. Mike Mosley returned after two crashes the previous day, and qualified solidly over 169 mph.

Third Day - Saturday May 22

A busy day saw the field filled to 33 cars car. The day concluded with Steve Krisiloff bumping out rookie Sam Posey.

Bump Day - Sunday May 23

Strong winds kept speeds down, and only three drivers successfully bumped their way into the field. The windy conditions led to six crashes, and hopefuls waited until the final 45 minutes before they took to the track. The session started out with Mel Kenyon bumping out Carl Williams. Bob Harkey bumped Dick Simon, and Art Pollard got back into the field by bumping Jim McElreath.

Jim Hurtubise once again tried to qualify his front-engined roadster, but on his second lap, hit the outside wall at the head of the main stretch. His first two laps would not have been fast enough to bump his way in. The day ended as Dick Simon (waved off) and Jerry Grant (waved off) made unsuccessful attempts.

After qualifying, car owner Dick Simon announced he was going to take over the machine qualified by John Mahler. By rule, the car must move to the rear of the grid (33rd) on race day.

Alternates

• First alternate: Jim McElreath (#14, #46)

Failed to Qualify

First half

Despite the pace car crash near the exit of the pits, the green light came on, and the race continued underway. Mark Donohue grabbed the lead from the middle of the front row.

On lap 12, Steve Krisiloff blew an engine, spilling oil in turn three. Mel Kenyon slid in the oil making contact with the turn three wall. Gordon Johncock and Mario Andretti continued to race each other through three yellow lights. When they arrived at turn three, track workers were on the scene beside the Kenyon machine. Having not heeded the yellow lights, both Johncock and Andretti slid in the oil with Johncock crashing into the Kenyon car, running over the top of it and destroying both cars. Kenyon, fortunately, had seen Johncock coming and dropped back down into the cockpit of his race car. Johncock's car left a tire mark on the top of Kenyon's helmet. The only injury received by Kenyon was a small cut on his shin from the dash board being pushed down onto his legs.^[25] All four cars were out of the race, and the yellow light was on for 19 minutes to clean up the accident.

Donohue led the first 50 laps, then the lead traded hands during pit stops between Joe Leonard, Bobby Unser, as well as Al Unser. After leading a total of 52 laps, Mark Donohue dropped out on lap 66 with broken gears. He came to a stop in turn four, and parked the car in the infield, just north of the entrance to the pits.

Lloyd Ruby led at the halfway point.

Second half

On lap 111, David Hobbs blew an engine on the main stretch. Rick Muther spun in the oil, his car veered to the inside wall, then bounced across the track, hitting Hobbs, and lifting up on two wheels. Hobbs' car was pushed head-on into the wall, but he was not seriously injured. Both cars slid down the main stretch, and came to a rest just beyond the start/finish line. The track was blocked except for a narrow portion on the inside where other cars were able to skirt by. The incident happened right in front of Al Unser, who was the leading the race at the moment. The yellow light came on for 12 minutes to clean up the crash.

After a series of pit stops by the leaders under the yellow, the green eventually came back out with Al Unser leading.

With less than 40 laps to go, Al Unser continued to lead, with Peter Revson second, Bobby Unser third, and A. J. Foyt fourth.

On lap 167, Mike Mosley lost a wheel in turn 4. He smacked the outside wall in turn four hard, then bounced across the track and hit the inside wall. Leader Al Unser was ahead of the crash, and second place Peter Revson just slipped by. Third place Bobby Unser spun to avoid Mosley, and hit the outside wall. Mosley's car then crashed into the parked cars of Mark Donohue and Steve Krisiloff, that were sitting near the entrance to the pits. A fire broke out, at which time 8th running^[26] Gary Bettenhausen stopped his car, and ran to the scene to help. Fire crews quickly doused the flames, and Mosley suffered a broken leg. Bill Vukovich II also spun to avoid the crash, but he was able to continue. The yellow remained on for 22 minutes to clean up the crash.

The green light came back on with less than 20 laps to go. Al Unser held a comfortable lead, and won his second 500 in a row. Despite four yellows for 53 minutes (about 48 laps), the average speed of 157.735 mph was a new record at the time. Bettenhausen, who finished 10th, was given a cheer at the finish for stopping to help Mosley and Unser on lap 164.^[27]

Race statistics

Radio

The race was carried live on the IMS Radio Network. It was carried on over 1,200 affiliates, including shortwave transmission to Europe, Asia, and Vietnam. The broadcast reached an estimated 100 million listeners worldwide. Sid Collins served as chief announcer and Len Sutton served as "driver expert." At the conclusion of the race, Lou Palmer reported from victory lane.

The entire on-air crew remained mostly consistent from 1966 to 1970. Bob Forbes was assigned as "wireless" microphone, covering the garages and roving reports. The pre-race coverage was 30 minutes long. In a departure from previous years, Sid Collins decided to eliminate booth interviews with celebrities during the race. The only exception was an interview with Hugh Downs, but that was during the post-race coverage. In addition, Luke Walton interviewed Evel Knievel in the pit area during the early stages of the race. Knievel was making his first visit to the 500, as a guest of the A. J. Foyt team.

Television

For the first time, the race was carried in the United States the same day the race was held, on ABC Sports on a same-day tape delay basis. The race was held in the afternoon, and the broadcast aired in prime time later in the day.

The broadcast totaled two hours, and came on-air at 8:30 p.m. (eastern). Among the notable appearances, was David Letterman, at the time employed by then-ABC Indianapolis affiliate WLWI, who served as a roving turn reporter. Letterman interviewed Mario Andretti after he dropped out of the race.

Chris Schenkel began what would be a decade-long tenure as host, while Jim McKay anchored the broadcast as play-by-play announcer. But Schenkel's day as host was short. Riding in (and broadcasting from) the pace car at the start of the race, he was slightly injured when the pace car crashed after coming into the pits at the start of the race.

The broadcast was re-aired numerous times on ESPN Classic from February 2002 until the network's shutdown at the end of 2021.