We have investigated the relationship between percentage fat mass and skinfold thicknesses in a group of male and female infants at 5, 11 and 26 weeks of age. Fat-free mass and hence fat mass was determined using an H218O dilution technique. Multiple regression analysis was used in order to evaluate whether the triceps and subscapular skinfold measurements, in a number of models, could predict percentage body fat. In all cases skinfold thickness was poorly predictive of percentage body fat. We suggest that variation in the distribution of internal and external stores of body fat may be a major factor accounting for the poor predictive value of skinfold thickness in this study.