It has been suggested that the early exposure to cow's milk protein may trigger the autoimmune response in IDDM. The objective of this case-control study was to evaluate the association between infant nutrition (breast feeding and exposure to cow's milk products) and the risk of IDDM. Infant nutrition data was collected in a structured questionaire in 50 diabetic children and 50 age-sex and district matched, healthy controls. Age of patients was (mean±SD) 12,23 ± 3,94 yr and 12,31 ± 3,89 yr for the control group. There were 23 females pairs and 27 males pairs. Results: in the diabetic group the prevalence of children who were never breastfed was larger(24% vs 4%, respectively), OR=7,5%; 95% CI=2,2-25,9;(p,0<05). Duration of exclusive breast feeding was shorter in the diabetic than in the control group(mean ± SD: 1,54 ± 1,69 vs 3,2 ± 2,07 mo; p<0.01). Age of introduction of cow's milk was smaller in the diabetic than in the control group (mean ± SD: 1,72±2,12 mo vs 3,58±2,34 mo; p<0.01). A larger proportion of diabetic children had been given cow's milk-based products before the age of 3 mo (64% vs 28%); OR= 4,57, 95% CI= 1,80 (p<0.01). These results are consistent with the hypothesis that breast-feeding and avoidance of cow's milk products during the three first months of age may reduce the risk of type I diabetes.