Changes in coital experience, birth control usage, and sex education between 1968, 1971, 1974, and 1978 were studied in unmarried Canadian university students. The percentage of coitally experienced females increased from 32% in 1968 to 58% in 1978 and of males from 40% to 62%. There was no significant change between 1974 and 1978 for either sex, nor were there sex differences in coital experience in either year. Coitally experienced females were more likely to have had intercourse in the 3 months preceding both 1974 and 1978 surveys, but otherwise there were no sex differences in coital frequency, lifetime number of coital partners, or age at first intercourse. Religion was a more reliable indicator of coital experience in 1968 than in 1978. Males were more likely than females to report postpubertal sexual contacts which they classified as homosexual (16.5% vs. 7%) whereas 12-13% of both sexes reported no sexual contacts of any kind with another person. Contraceptive risk-taking was high at first intercourse and among those having infrequent coitus. However, both this group and more coitally active students were less likely to take such risks in 1978 than in 1968, almost entirely because of increased pill use. Coitally experienced vs. inexperienced students differed in their ranking of the major influences on their knowledge and attitudes about sex.