Our main objective has been geared toward the appreciation of the importance of the infection by human immunodeficiency virus in Mali. Our study was based on 3,496 sera deducted from March 1987 to January 1989. All positive sera at ELISA have been confirmed by Western Blot. The total seroprevalence of the study is 8.41%. This fact has been noticed higher in prostitutes, young men, more in women than in men in widows and divorced couples, in traders, in travellers of high endemic countries. The seropositivity is proportional to the number of sexual partners. The heterosexual way of transmission has been dominant. There has been no relationship between seropositivity and transfusion, antecedent of surgery, sexually transmitted diseases, of sexual intercourse type. The HIV2 has been more frequent than HIV1. Taking into account the importance of this infection, precautionary measures must be taken to avoid an evolution toward a catastrophic situation.