In order to assess the seroprevalence and coprevalence of hepatitis-B surface antigen (HBsAg), human immunodeficiency virus-1 and -2 (HIV-1 and -2) antibodies in Nigerian children with/without protein energy malnutrition (PEM), we studied plasma specimens of 206 children with PEM and 200 apparently healthy reference children aged between 1 and 3 years by enzyme-linked immunosorbent assays (ELISA). HIV-seropositive cases were confirmed by immunoblotting (IB). Of the children studied, eight (4%) of the healthy and four (1.9%) of the malnourished (P = 0.22, Fisher's exact test) were positive for HIV-1 antibodies, 40 (20%) of the healthy and 54 (26%) of the malnourished (P = 0.14) were positive for HBsAg, and five (2.5%) of the healthy and four (1.9%) of the malnourished (P = 0.70) were positive for both HIV-1/HBsAg. No case of HIV-2 antibodies was found. While the seroprevalence of HBsAg was higher in the malnourished subjects, the reverse was the case with HIV antibodies. However, all the four HIV-1-positive malnourished children and five of eight of the HIV-1-positive reference children were simultaneously positive for HBsAg. This is the first epidemiological report on the seroprevalence and coprevalence of HIV and HBsAg in apparently healthy and malnourished Nigerian children.