Human immunodeficiency virus (HIV) strains can be separated into two serotypes: HIV-1 and HIV-2. In the study reported herein, we developed and evaluated competitive enzyme-immunoassays (CEIA-1 for the detection of antibody to HIV-1, CEIA-2 for the detection of antibody to HIV-2) to discriminate serologically between HIV-1 and HIV-2 infections. In most of the cases, the serotyping of known reactive serum samples was done easily with the CEIAs, showing a similar specificity to the Western blot. Such competitive assays could represent alternative procedures for serotyping HIV infection and would limit the need for expensive Western blots, especially in economically poor countries.