Fifty-five children previously investigated for failure to thrive (a rate of weight gain below -2 SD) during at least 6 weeks at 4-18 months of age were followed up and reinvestigated at the age of 4 years. The children were studied in two groups: children with organic causes (OFTT) (n = 21); and children for whom no organic cause was found (nonorganic failure to thrive, NFTT) (n = 34). In children with OFTT, normalization of growth was found for both weight and height attained, as most of the diseases were either amenable to treatment or spontaneously subsided. The only exception was a child with severe encephalopathy. In children with NFTT, much lower values were found, particularly for weight, p less than .01 for both weight and height. Children with a low psychosocial score (less than or equal to 3 adverse factors) showed partial catch-up growth, although significantly lower than that of children with OFFT. Among 13 children with high psychosocial scores (greater than or equal to 4), 6 children had been subjected to strong social and/or psychological intervention. These children showed a more favorable growth pattern compared to children with comparable psychosocial scores where no intervention had been undertaken. The children with NFTT continued to grow slowly, remained meager and seemed to maintain a suboptimal growth pattern, particularly those with higher numbers of risk factors.