Four peptides of human immunodeficiency virus (HIV) located in the regions of gp41, gp120, p24 of HIV-1 and gp36 of HIV-2 have been synthesized according to the published amino acid sequences and the positions of antigenetic determinants of viruses by a solid-phase method. An indirect ELISA for detecting antibody against HIV 1/2 was established using these synthetic peptides as the coating antigens. We detected 41 control sera provided by National Institute for the Control of Pharmaceutical and Biological Products. The results indicated that the general coincident rate were 100%, the variant coefficient was less than 10%. A comparison of our reagent with Huayi, Pasteur and Jinhao reagents in detection of 90 positive sera and 140 normal sera for HIV-1/2 showed that the coincident rate was 100% with Pasteur and Jinhao, 99.57% with Huayi. All of 186 sera from patients with other diseases were negative. The reagent are stable at 37 degrees C for 4 days. The results indicated that our reagent is highly specific, sensitive and stable, it can be used for detection of HIV-1/2 infections.