A familial predisposition has been proposed as a major determinant of the increased morbidity and mortality from cardiovascular disease demonstrated in Type 1 (insulin-dependent) diabetic patients with nephropathy. We assessed this concept by studying 91 parents of Type 1 diabetic patients with nephropathy and 94 parents of aged-matched Type 1 diabetic patients with normoalbuminuria. The two groups of parents were of a similar age (58 +/- 8 vs 58 +/- 7 years). The prevalence (%) of death and cardiovascular diseases (World Health Organisation questionnaire) was 10 (4-18)% and 12 (6-21)% in parents of nephropathic patients compared to 8 (3-16)% and 13 (6-23)% in parents of normoalbuminuric Type 1 diabetic patients. The frequency of risk factors for cardiovascular disease were about the same in both groups of parents. Microalbuminuria was found in 5% and 11%, hypercholesterolaemia (greater than 6.5 mmol/l) in 25% and 26% and smokers constituted 40% and 34% of parents of patients with and without proteinuria, respectively. A familial predisposition to cardiovascular disease cannot explain the increased morbidity and mortality from cardiovascular disease in young patients with diabetic nephropathy.