consequences, and university students are at increased risk. The aim of this study was to determine the trend of sexual behaviour among first year students at School of Medicine, University of Zagreb, Croatia. Methods: Retrospective study included first year medical students, from academic year 2008/2009 to 2018/2019. Data were collected by anonymous questionnaire each academic year, and analysed by descriptive (χ2 test, Fisher's exact test) and analytical statistics (simple linear regression model using the least squares method, t-test) with a significance level of α = 0.05. Results: Data analysis included a total of 3155 medical students (96.7%), 62.6% girls. The number of students who had sexual intercourse varied across generation from 47.9% in 2008/2009 to 42.5% in 2018/2019, with significant difference between 2011/2012 and 2016/2017 (49.6% vs 37.1% ; P=0.004). The mean age of the first intercourse showed stable trend across generation, and ranges from 16.93±1.34 years in 2008/2009 to 17.23±1.12 years in 2018/2019. Mean number of sexual partners ranges from 1.76±1.42 in 2008/2009 to 2.00±2.54 in 2018/2019, without statistically significant difference among generations of students from the academic year 2008/2009 to 2018/2019. The highest number of sexually active students in all generations from 2008/2009 to 2018/2019 used contraception always, and showed stable trend across generations, without significant difference. Conclusion: Results showed stable trend of responsible sexual behaviour among first-year medical students in the eleven-year period. Further studies are needed in order to estimate risk behaviour among non-medical students.