To investigate the association between the family environment and metabolic control of childhood diabetes 20 diabetic children aged between 4 and 12 years with same-sex healthy siblings and two cohabiting parents were selected. The parents were interviewed separately and completed questionnaires about their own and their spouse's involvement and shared activities with both children, diabetic management, and knowledge of and attitudes towards diabetes. They also completed the Moos Family Environment Scale (FES) which yields ten sub-scales relating to different aspects of family functioning as did 20 sets of parents with age- and sex-matched healthy children, who also completed questionnaires concerning their involvement and shared activities with their children. There were no differences between the families of diabetics and of controls in the extent to which either parent was involved with their children or in the attention each child received. Fathers of diabetic children differed from controls in their use of punishment and diabetic families were less achievement oriented. The degree of metabolic control (HbA1 assessment at three-monthly intervals) was related to parental involvement with the non-diabetic child and to some aspects of the FES including parental incongruence. These differences in family functioning suggest useful directions for possible intervention programmes.