Having boys or girls is essentially random and doesn't depend on the parents' genes, researchers report.

Protein levels in a drop of blood can accurately predict someone's age, researchers say. The discovery sheds new light on how we age differently.

Same-sex behavior in animals is not only "not costly" from a natural selection perspective, but it also may have important benefits.

Cisgender children tend to gravitate toward the toys, clothing, and friendships stereotypically linked with that gender. Transgender children do the same, research finds.

"[C]hildren's brains function similarly regardless of their gender..." according to a new neuroimaging study on math ability in boys and girls.

The elbow may offer a better way to determine the sex of a skeleton in some populations, researchers report.

Men account for less than 1% of all breast cancer cases, but their five-year mortality rate is 19% higher than that of women, according to a new study.

Evaluating mild cognitive impairment, considered a precursor to dementia, by sex could potentially change who gets the diagnosis.

Researchers have identified a stress-activated depression circuit that drives different behavior in male and female mice.

New research links chronic mid-life stress, though not trauma, with memory decline in women. That link did not appear for men.