Sexual behavior change is a complex issue influenced by complex variables, intrinsic and extrinsic. This study aimed to assess factors influencing actual use of a male condom among secondary school students in southern Tanzania. In all, 227 sexually experienced participants aged 14 to 18 completed a pretested questionnaire. Out of 227 sexually active participants, 120 (53%) reported consistent condom use and (62.5%) had multiple sexual partnerships. Of 120 who reported condom use, 42 (35%) had tested for HIV. Among males, age was positively correlated with actual condom use, while being a Catholic and having multiple concurrent sexual partners were negatively correlated with actual condom use. Among females, being a Protestant was positively related with actual condom use, while being a Catholic, reporting multiple sexual partnerships, and perceived barriers to condom were negatively correlated with actual condom use. In conclusion, sexually active youth in this population practice risky sexual behaviors, with a low proportion of condom use. Efforts are warranted to motivate sexually active youth to engage in HIV prevention, including condom use and HIV testing. (MPH) is a lecturer and research fellow, currently with KCMC-DUKE University AIDS Program, Kilimanjaro Christian Medical Centre, Moshi, Tanzania.Victoria Mwakalo (Bsc Nursing) is a nurse officer, currently with Rungwe District Hospital, Mbeya, Tanzania.Declare Mushi (PhD) is a senior lecturer and research fellow, currently with Kilimanjaro Christian