Infection with the human immunodeficiency virus (HIV) remains a public health concern worldwide. Young adults are the most commonly affected by the pandemic, 40% of new cases involving persons aged between 15 to 24 years. This age group is the most -sexually active. There are four opportunities for HIV prevention. Post-exposure prophylaxis (PEP) by administering anti-retroviral treatment is a prevention tool in a post-coital setting for exposed patients. The probability of HIV transmission depends on the type of exposure, infectivity level of the source, and susceptibility of the person exposed. The risk for a person to acquire HIV following an exposure incident can be calculated by multiplying the risk that the source person is HIV positive by the risk associated with a particular exposure. Prophylaxis is recommended when the risk of transmission is greater than 1/1000, and prophylaxis should be considered when the risk is between 1/1000 and 1/10 000. When this risk is less than 1/10 000, prophylaxis is not recommended. The most recent guidelines recommend administering two nucleoside reverse transcriptase inhibitors (NRTI) associated with either an integrase inhibitor (INI) or a boosted protease inhibitor (PI / r). The treatment should be initiated as soon as possible after exposure, preferably within 24 h, but can be considered up to 72 h. The duration the treatment is 28 days; HIV status should be performed on Day 0 and at 8 weeks with a 4th generation blood test. Lastly, during follow-up, counseling on HIV prevention should be provided.