RESUMEN
<p><b>INTRODUCTION</b>This study aimed to investigate the determinants of sexual intercourse initiation among incarcerated adolescents aged 12-19 years in Malaysia.</p><p><b>METHODS</b>This was a sequential mixed-method research project that was conducted in two phases. Quantitative and qualitative methods were used in the first and second phases, respectively. Data was collected via a survey using self-reported questionnaires from 1,082 adolescents, and from in-depth interviews and the written essays of 29 participants. The participants were recruited from 22 welfare institutions in peninsular Malaysia.</p><p><b>RESULTS</b>Among the study participants, 483 were male and 599 were female. Overall, 62.3% of the incarcerated adolescents had initiated sexual intercourse at least once. The mean age at first sexual intercourse for both genders was 14.0 years. Individual factors found to be associated with previous sexual intercourse were the female gender (odds ratio [OR] 1.75; 95% confidence interval [CI] 1.11-2.74), previous alcohol use (OR 1.80; 95% CI 1.10-2.94), previous illicit drug use (OR 1.85; 95% CI 1.07-3.22), permissive attitude toward premarital sex (OR 4.34; 95% CI 2.17-8.70), and sexual abuse during childhood (OR 5.41; 95% CI 3.52-8.32). Qualitative findings revealed that the reasons for initiation of sexual intercourse among these adolescents were partner influence, inability to control sex drive, family issues, and the perception of sex as an expression of love.</p><p><b>CONCLUSION</b>The determinants of sexual intercourse initiation among incarcerated Malaysian adolescents are comparable to those of developed countries. However, in Malaysia, sexual and reproductive health programmes for such adolescents should be tailored to address their specific needs.</p>