Risky sexual behaviours are linked to a higher likelihood of transmitting sexually transmitted infections (STIs). These behaviours include having multiple sexual partners, engaging with sex workers and having sex with individuals who inject drugs, as they increase the risk of STIs. Furthermore, situations such as unprotected sex and oral sex also qualify as risky sexual behaviours. People of any sexual orientation may engage in oral sex, which is reported to be associated with STIs such as gonorrhoea, herpes, syphilis and human immunodeficiency virus (HIV). Oral sex can also potentially spread human papillomavirus virus (HPV) and chlamydia infections. This chapter discusses various risky sexual behaviours, their possible associations with oral diseases and the methods involved in their diagnosis. The dentist’s role in diagnosing and preventing STIs is also examined.