This study was designed to examine the hypothesis that some environmental factors increase the risk for insulin-dependent diabetes mellitus. Data on dietary history was collected from 80 diabetic children from the Santiago de Chile Registry and from 85 nondiabetic control subjects who were comparable in terms of age, sex, and ethnic characteristics. Early exposure was defined as the ingestion of food sources other than maternal milk before 3 months of age. To define genetic susceptibility to insulin-dependent diabetes mellitus each subject was typed in terms of HLA DQA1 and DQB1, and the possible conformation of susceptible heterodimers was considered as a risk marker. Fewer children were exclusively breast fed in the diabetic group than in the control group (21.55±15.05 vs. 33.95±20.40 weeks, P<0.01). in="" addition,="" exposure="" to="" cow's="" milk="" and="" solid="" foods="" occurred="" earlier="" in="" the="" diabetic="" group="" than="" in="" the="" control="" group="" (15.90±10.95="" vs.="" 21.15="" 13.65="" and="" 16.85±10.25="" vs.="" 21.20±12.35="" weeks,="">P<0.05). our="" data="" show="" that="" a="" short="" duration="" of="" breast-feeding="" and="" early="" exposure="" to="" cow's="" milk="" and="" solid="" foods="" may="" be="" important="" factors="" in="" the="" development="" of="" insulin-dependent="" diabetes="" mellitus.="" the="" high="" relative="" risk="" observed="" in="" individuals="" genetically="" predisposed="" indicates="" an="" interaction="" effect="" between="" genetic="" and="" environmental="">