AimTo assess the prevalence and dynamics of risky sexual behaviors among Croatian emerging adults in the 2005-2021 period.MethodsThree surveys were conducted on large-scale national samples of young adults aged 18-24 in 2005 (N = 1092) and 18-25 in 2010 and 2021 (N = 1005 and N = 1210, respectively). The 2005 and 2010 studies were conducted with face-to-face interviews on stratified probabilistic samples. The 2021 study was conducted by computer-assisted web-interviewing on a quota-based random sample from the largest national online panel.ResultsCompared with 2005 and 2010, the age at coital debut increased for both genders in 2021 (by a median of one year, to 18 years, and by a mean of half a year, to 17.5 years, in men and to 17.9 in women). In the 2005-2021 period, condom use increased by about 15% both at first intercourse (to 80%) and in consistent use (to 40% in women and 50% in men). When we controlled for basic socio-demographics, Cox and logistic regressions indicated that, for both genders, in 2005 and 2010 compared with 2021, the risks/odds were significantly higher for reporting an earlier sexual debut (adjusted hazard ratio 1.25-1.37), multiple sexual partners (adjusted odds ratio [AOR] 1.62-3.31), and concurrent relationships (AOR 3.36-4.64), while the odds were lower for condom use at first sexual intercourse (AOR 0.24-0.46) and consistently (AOR 0.51-0.64).ConclusionRisky sexual behaviors decreased in the 2021 survey compared with the previous two waves, in both genders. Nonetheless, sexual risk-taking is still frequent among young Croatian adults. The introduction of sexuality education and other national-level public health interventions to reduce sexual risk-taking thus remains a public health imperative.