The authors conducted a matched case-control study in Germany to identify risk factors for sporadic illness associated with Shiga toxin-producing Escherichia coli (STEC) infection, regardless of serogroup. From April 2001 through March 2003, cases were prospectively enrolled through a laboratory-based sentinel surveillance system located in 14 of the 16 German federal states. One control was identified per case, matched by age and region. Conditional logistic regression was used in the analysis, which was conducted separately for three age groups (<3 years, 3-9 years, and > or =10 years). The median age of the 202 enrolled cases was 2.5 years (range, 3 months-89 years). Hemolytic uremic syndrome developed in five patients. Non-O157 strains accounted for 85% of the isolated STEC. In children under 3 years of age, having touched a ruminant had the highest odds of disease, and raw milk was the only food identified as a risk factor. In contrast, in persons aged 10 years or older, only food items (i.e., lamb meat, raw spreadable sausages) were significantly associated with illness. In this study, risk factors were age-specific. Direct transmission through food played a lesser role in children under 3 years of age, the population at greatest risk of both acquiring STEC infection and developing hemolytic uremic syndrome.