Several dimensions of parent-child relationships were examined as predictors of adherence to treatment and metabolic control in a multi-informant study of 88 children and adolescents with insulin-dependent diabetes mellitus who were recruited from 2 endocrinology clinics. Ratings of parent-child discipline, warmth, and behavioral support were not significantly associated with diabetes outcome, but parent-child conflict was a consistent correlate of both adherence and metabolic control. Within a public hospital subsample, conflict was related to parent, child, and nurse ratings of adherence and to a physiological index of metabolic control. These results were partially replicated in a private practice sample where conflict was significantly related to parents' ratings of adherence and to metabolic control. Conflict accounted for unique variance in diabetes outcome beyond that associated with other measures of the parent-child relationship, but the relation between conflict and metabolic control was no longer significant when adherence ratings were entered into regression equations first.