The medical records of 142 infants referred for evaluation solely because they were born to human immunodeficiency virus (HIV)-infected mothers (i.e. not because of signs or symptoms suggesting HIV infection), were reviewed. The infection status of 85 of these infants has been determined; 17 (20%) have confirmed HIV infection and 68 have seroreverted to HIV and lack evidence of infection. During the first 6 months of life HIV culture had better sensitivity, specificity, positive predictive value and negative predictive value for diagnosis of HIV infection than did physical examination, serum immunoglobulin determination or HIV p24 antigen determination. Of the 16 HIV-infected infants who were available for evaluation during the first 6 months of life, all had at least one culture from blood positive for HIV. Two of 4 and 10 of 11 infants were culture-positive at birth and during the first 3 months of life, respectively. A positive HIV culture result was the earliest finding of infection in 15 infants; 10 of these infants concomitantly were found to have hyperimmunoglobulinemia (8 cases) and/or an abnormal physical examination (4 cases). One HIV-infected infant developed hyperimmunoglobulinemia G and A at age 3 months without other evidence of HIV infection until age 5 months when a positive HIV culture was noted. All HIV-infected infants had abnormal findings by physical examination, a positive HIV culture, and/or hyperimmunoglobulinemia by 3 months of age. Infants with normal physical examination and laboratory test results at 3 and/or 6 months of age invariably were HIV-uninfected.