In a longitudinal study of weight and height over the first 4 years of life, 123 human immunodeficiency virus (HIV)-infected and 654 uninfected children of similar social background were compared. By 3 months of age there was a 400-g (8.0%) difference in weight and an 0.8-cm (1.3%) difference in height between infected and uninfected children. After age 1 year the differences stabilized and infected children were, on average, approximately 6% less heavy and 2% shorter than uninfected children. Most of the weight difference was explained by differences in height, particularly after age 1 year. Although statistically significant the difference between infected and uninfected children was small. Weight and height measurements were not useful indicators of infection. Before 6 months of age differences in weight velocity could not be explained by HIV-related morbidity and might have been related to a primary HIV infection. At older ages growth failure associated with HIV infection could be attributed to secondary HIV-related morbidity.