We appreciate Dr. Pick's interest in our paper on dissimilar sized twins. It may be as Dr. Pick suggests that some infants of small birth weight for their gestational age grow and develop "normally." Our study has demonstrated the failure of the undersized member of twin pairs to achieve a comparable level of growth and development to that of the co-twin at the time of the study examination. The reasons for this continued disproportion in size are not clear. Further studies are necessary to relate all possible factors concerned in intrauterine growth retardation with the subsequent development of the child.