The restless legs syndrome (RLS) occurs in adulthood with a prevalence of 5 to 10% and can be associated with diabetes mellitus. The prevalence in childhood, however, is unknown. We asked consecutive children with type 1 (insulin-dependent) diabetes mellitus as well as their parents and siblings about RLS according to a standardised questionnaire. Altogether, 46 patients (25 female, 12.0 +/- 3.7 years), 50 siblings (29 female, 12.3 +/- 5.5 years) and 75 parents (41 mothers, 40.4 +/- 5.1 years; 34 fathers, 42.5 +/- 5.3 years; 1.3 % with diabetes mellitus) were included. One patient (2.2%), one sibling (2.0%), and 14 parents (18.7%) were diagnosed as having RLS. Disturbances of sleep initiating, sleep maintenance and daytime tiredness were similar in patients and siblings. There was a significant association of higher HbA1c values (mean 7.7 +/- 2.2%) with sleep initiating problems. The mean dose of international units of insulin/kg body weight/day (0.79 +/- 0.26 IU) was not associated with the presence of RLS or sleep problems. To conclude, there seems to be no association of diabetes mellitus type 1 with RLS in children and adolescents. However, there is a relationship between diabetes and sleep disturbances and an optimally controlled diabetes mellitus might be an important factor for an improved sleep initiation.