By analysing data randomly collected via administration of questionnaire by interview of individuals on sexual risk behaviour to 628 young people living in Osogbo, Nigeria, the results of the questionnaire revealed that the mean age of first sexual encounter was 17.4 years for men and 16.5 years for women. Men tended to have multiple sexual partners more than the women (74.4% and 25.1%, respectively), while there was a highly significant relationship between sexually transmitted disease and multiple sexual partners among singles with P<0.001 and P= 0.000. We concluded that parents and government alike should teach sex education at home, and in schools involving intensive counselling.