Pre- and postoperative growth was analyzed in 22 children with craniopharyngioma. In 19 children a growth failure preceded the diagnosis by a mean of 4 years. Six children were obese preoperatively. During the first 3 postoperative months relative weight increased greater than 10% in 14/21 children (there was one surgical death). One year after surgery 13/21 were obese. Neither the size of the tumor nor the mode of surgery was decisive in the development of the obesity. Serum insulin and insulin-like growth factor I (IGF-I) were assessed in four children with growth hormone deficiency (GHD) who, after surgery for craniopharyngioma, were growing normally without GH substitution. One of them was normal in weight and had normal insulin and IGF-I levels; the others were obese and had supranormal insulin and subnormal IGF-I levels. One of the four and two other children with unsubstituted GHD reached final height SDS -0.8, -2.0 and -2.4. One child with normal postoperative GH response reached final height SDS -0.7. Final height SDS greater than or equal to -2.5 was gained with GH substitution by 6/11 children. It was greater than 2.0 SD below the height SDS expected from the heights of the parents in 7/11. An adequate monitoring of children's growth would lead to earlier diagnosis and probably better outcome.