This study examined sharing of diabetes responsibilities between mothers and their diabetic children and the relationship between patterns of mother-child sharing of responsibility for diabetes tasks and demographic variables, adherence, and metabolic functioning in children with insulin-dependent diabetes mellitus (IDDM). A factor analysis of the Diabetes Family Responsibility Questionnaire (DFRQ), a 17-item questionnaire developed for the present study, resulted in a meaningful three-factor solution. Factors included responsibilities related to regimen tasks, General Health Maintenance, and Social Presentation of Diabetes. Analysis indicated that the DFRQ had adequate internal consistency and concurrent validity. One hundred and twenty-one children with IDDM, 6-21 years of age, and their mothers completed the DFRQ. Glycosylated hemoglobin (HbA1c) was used to index the child's level of metabolic control. Results of multiple regression analyses indicated that the child's age, disease duration, and sex are significant predictors of mother and child patterns of sharing diabetes responsibilities. Disagreements between mothers and children in perceptions of who is assuming responsibility and adherence level were significant predictors of HbA1c. Results indicated that children assume increasing responsibility with increasing age. Clinicians should not assume that mothers and children communicate about the sharing of diabetes responsibilities in the family or about changes in expectations of who is responsible as children develop. To foster better control and adherence in diabetic children, members of the health care team can help to identify diabetes tasks for which no one in the family takes responsibility.