Every 10 years from 1980 to 2010, students in a British Columbia university were surveyed about age of sexual initiation, number of partners, and degree of emotional intimacy within their partnerships. Between 1980 and 1990, the socially acceptable prerequisite for premarital sex appeared to shift from the promise of marriage to mutual love. This change was demonstrated by a fall in the virginity rate among unmarried females, and the rise of monogamous romantic relationships for males. From 1980 through 2010, men reported more sexual partners than did women, with a smaller, though rising, proportion of serious relationships. Since 1990, never-married students were classified into three sexual behavioural groups: monogamists (about 55%), abstainers (30%), and multi-partnered “experimenters” (20% of men throughout each decade, and 7.6% of women in 1990–2000, rising to 14.4% in 2010). Experimenters generally reported concurrent partners, most of them casual. Since 1980, most sexually active students have experienced both romantic relationships and casual sexual partnerships, yet since at least 1990, the majority have been primarily monogamous. This article traces the changes and continuities in romantic relationships, casual sex, and sexual behavioural groups over 30 years, concluding that contrary to the claims of popular media and some academics, casual sex (“hookup culture”) has not replaced romantic relationships as the most common form of student sexual behaviour.