OBJECTIVE To compare the growth curves based on measurements of body weight for male and female infants dying of sudden infant death syndrome (SIDS) with those of male and female controls. METHODS The data were drawn from a large case control study of SIDS carried out in New Zealand between 1987 and 1990. RESULTS The mean birthweight for the cases was 3049 g and for the controls 3526 g. The mean growth curves for the male and female controls were close to the 50th centile of growth charts used in New Zealand. The growth curve for the male cases diverged from that of the controls, being closer to the 25th percentile. The differences between the female cases and controls were less pronounced. The differences in weekly weight increments derived from the curves for the cases and controls for nine 4-week periods were not statistically significant after taking into account race, manner of feeding and maternal smoking for any 4-week period. CONCLUSIONS SIDS cases were lighter at birth, but their growth velocity was normal postnatally.