OBJECTIVE: A familial predisposition was proposed to be a determinant of the increased morbidity and mortality from cardiovascular disease in type 1 diabetic patients with diabetic nephropathy. The insertion allele of an insertion/deletion polymorphism in the ACE (ACE/ID) gene seems to protect against coronary heart disease in nondiabetic and diabetic subjects. The aim of the present study was to evaluate these hypotheses in parents of a large group of type 1 diabetic patients with and without diabetic nephropathy. RESEARCH DESIGN AND METHODS: We investigated cardiovascular morbidity and mortality of parents of 163 type 1 diabetic patients with nephropathy and parents of 163 sex- and age-matched normoalbuminuric patients with type 1 diabetes. RESULTS: Kaplan-Meier curves showed that total parental mortality was significantly increased in parents of type 1 diabetic patients with nephropathy (121 of 244 [ approximately 50%] ) as compared with parents of normoalbuminuric type 1 diabetic patients (119 of 269 [approximately 44%]) (P = 0.008 [log-rank test]) partially due to an increase in cardiovascular deaths (48 of 244 [approximately 20%] vs. 42 of 269 [approximately 16%], P