This study was undertaken to ascertain a clinical impression that the prevalence of complications is higher in insulin-dependent Algerian diabetics than in their European counterparts. Forty-one Algerian patients under regular follow-up for 2 years or more were closely matched to 41 French insulin dependent diabetics with regard to sex (34M/7F) and duration of disease (10.5 +/- 1 year; range 2 -32 years). Insulin dose, number of injections, arterial blood pressure, glycemia, glycosylated haemoglobin, cholesterolemia and triglyceridemia were similar in the two groups. The age at the time of diagnosis of diabetes was higher in the Algerian group (28.7 +/- 1.9 vs 21.4 +/- 1.7) as was the number of smokers (23/41 vs 12/41). No difference was noted between the two groups with respect to the prevalence of retinopathy (absent, simple, proliferative): 25, 12, and 4 vs 29, 9, and 3 or nephropathy (absent, incipiens, patent): 30, 6, 5 for the Algerians and 35, 3, 2 for the French. This suggest that long term metabolic control was relatively identical in the two groups. The incidence of neuropathy rated as absent, moderate (abolished reflexes, impaired pallesthesia, cardiac neuropathy) or severe was significantly higher in the Algerians (13, 16 and 12) as compared to the French (28, 10 and 3) p less than 0.01. Severe neuropathy in the Algerian group was often multiple (8/12), serious and early. The only difference between the neuropathic and non-neuropathic Algerian subgroups was the duration of disease (13.2 +/- 2.2 vs 7.3 +/- 0.01; p less than 0.01). Since there were apparently no acquired nutritional factors, an ethnic predisposition of Algerians to develop neuropathy seems likely.(ABSTRACT TRUNCATED AT 250 WORDS)