Diet is recognized to play a role in the occurrence of breast cancer; however, the data are inconsistent. The goal of this study was to determine the influence of dietary factors on breast cancer risk among women up to 50 yr of age in a German population. A population-based case-control study was conducted including 706 cases and 1,381 controls. In addition to a risk factor questionnaire, a subgroup of 355 cases and 838 controls completed a food frequency questionnaire. Breast cancer risk was inversely associated with vegetable consumption (P for trend = 0.034). The odds ratio for the fourth quartile of vegetable intake compared with the first quartile was 0.64 (95% confidence interval = 0.43-0.96). Breast cancer risk increased with a higher consumption of red meat (P for trend = 0.016); women with the highest consumption level had an 85% elevated breast cancer risk compared with the lowest quartile (95% confidence interval = 1.23-2.78). When only premenopausal women were considered, the protective effect of vegetable intake and the positive association with meat intake were even stronger. These results are compatible with the international recommendations for a breast cancer preventive diet and suggest that the favorable effect of a diet high in vegetables and low in red meat, especially beef, may be stronger in premenopausal women.