Two groups of babies, one having SMA, one homogenised milk, were studied. Haemoglobin was measured in the neonatal period, and at 3, 6, 10 1/2 and 15 months. Five babies of the homogenised milk group became anaemic. Stools were tested for occult blood, with more strongly positive test results found in babies having homogenised milk. Serum lipids were measured at 3, 6, 10 1/2 and 15 months. Serum cholesterol was significantly higher at three and six months in the homogenised milk group. There were no significant differences in growth between the groups. Review of progress at five years of age discovered higher serum cholesterol in those children of social class three who had homogenised milk compared with the similar five year olds who had had SMA.