Childhood diabetes is most common in Nordic countries and its incidence is rising. In order to evaluate the efficacy of health care follow-up units we investigated physical and psychosocial health status, mode of coping with adult health care and medical treatment in 82 young adults (46 males, 36 females, average age 20.9 yr. and average disease duration 12.7 yr.) who had had diabetes since childhood. All but three of them made regular visits to a health care facility but only 27% monitored blood glucose reasonably well. Only eight percent had a HbA1 concentration within the optimal range, and half had a inappropriate level. Half of the subjects with high HbA1 in adolescence had managed to improve it since leaving the paediatric unit. The most common clinical findings were lipohypertrophy and depressed patellar and achillar reflexes. Up to 70% had background retinopathy and 10% proliferative retinopathy, while two thirds (62%) had depressed conduction velocity of the peroneal nerve. Clinically significant psychiatric problems were found in 17% of the patients, depression being the most prominent feature. Among the social characteristics, delayed social maturation and lack of vocational education were found to be more common than in age-matched controls. One in three exhibited a major overt physical problem and one in five a major psychosocial problem. In conclusion, whatever the health care follow-up unit attended by young adults with diabetes since childhood, the teams face health problems that differ totally from one individual to another. It is important at this transitional age to focus attention in a broad-minded manner on the many factors complicating diabetes or affecting good compliance with treatment.