The aim of this study was to investigate the relationship between maternal HIV status and the anthropometric characteristics of children at birth. A cross-sectional study was conducted in Bobo-Dioulasso from January 1995 to May 1996. We included all mother-child pairs seen postpartum for whom the HIV status of the mother had been determined at an antenatal visit and anthropometric measurements had been taken for the child at birth. Birth weights below 2,500 g were classed as "low", body lengths of less than 47 cm at birth were described as "small birth size" and head circumferences of less than 33 cm were classed as "small". We included 956 mothers and 956 children in the survey. Low birth-weights were recorded more frequently among children born to HIV-infected mothers than among those born to uninfected mothers (23. 37% versus 15.6%; p = 0.006). Mean birth-weight, birth size and head circumference did not differ significantly between the children of HIV-infected and uninfected mothers. In multivariate analysis, HIV infection and primiparity were independently associated with low birth-weight. Maternal HIV infection was the only factor associated with small birth size. There was no relationship between head circumference and maternal HIV status. Thus, maternal HIV infection appears to be associated with low birth-weight and small birth size.