The Acquired Immune deficiency Syndrome (AIDS), caused by the Human Immunodeficiency Virus (HIV) is now a worldwide social problem. Routine diagnostic procedures to identify infected individuals are based on the presence of antibodies against viral epitopes in the serum. There is nevertheless impelling need to detect directly the virus in people infected by HIV, independently of a serological response. In this study we describe the procedure which allows amplification of a specific segment of the HIV genome, through the Polymerase Chain Reaction (PCR), in infected individuals. This new approach represents a precious tool towards the diagnosis of HIV infection, it can be easily and quickly carried out on a large scale and will be capable of identifying HIV infected subjects before the development of antibodies.