Malnutrition compromises the growth of children in sub-Saharan Africa. In Nigeria, the prevalence of childhood malnutrition approaches 40%. There are few reports relating the growth characteristics of breast-fed Nigerian infants to the anthropometric properties of their mothers. A total of 100 urban and rural mother/baby pairs were recruited. The mean BMI values of the urban and rural mothers were 24.2 and 21.3 kg m(-2), respectively. The mean length, weight and head circumference of the rural infants were significantly lower than those of the urban infants. Z-scores based on World Health Organization standards showed: (i) length-for-age z-score <-2 in urban (27%) and rural (33%) children; (ii) a higher incidence of underweight and small HC in rural (33%; and 13%) versus urban children (12% and 0%); and (iii) positive correlations between all three z-scores and maternal BMI. Negative correlations were observed between infant age and z-scores for length-for-age, weight-for-age and HC-for-age.