An energy-dense supplementary food, together with nutrition education, was given to a group of moderately malnourished children aged 6-12 months in a poor slum community of urban Bangladesh. An age- and sex-matched control group received only nutrition education. Both groups were followed monthly with respect to weight gain and morbidity. The purpose of the study was to assess the differential impact of a targeted supplementary feeding programme with nutrition education and a nutrition education programme alone on monthly weight gain during 6 months. During the 1st 3 months of the intervention, the monthly weight gain of the supplemented children was 205 g vs 159 g in the control children (p less than 0.05). In the following 3 months, differences in weight gain were no more significant. Several possible explanations for this transient impact are discussed. It is suggested that nutrition education in the control group may have been responsible for the limited difference between the two groups, but seasonal and epidemiological factors may also have played a part.