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During an epidemic of cholera in Guinea, West Africa, in 1986, the authors conducted two studies of risk factors for transmission. In the capital city, 35 hospitalized cholera patients were more likely than 70 neighborhood-matched controls to have eaten leftover peanut sauces (odds ration (OR) = 3.1, 95% confidence interval (CI) 1.2-8.2), but less likely to have eaten tomato sauces (OR = 0.2, 95 percent CI 0.1-0.9). Hand washing with soap before meals by all family members protected against cholera (OR = 0.2, 95 percent CI 0.02-0.96), suggesting that persons asymptomatically infected with Vibrio cholerae 01 may have been the initial source for contamination of the leftover foods. Laboratory studies demonstrated that V. cholerae multiplied rapidly in peanut sauce (pH 6.0), but not in the more acidic tomato sauce (pH 5.0). In an outbreak of cholera-like illness after a rural funeral, illness was strongly associated with eating a rice meal served over many hours without reheating. These studies demonstrated that, in this epidemic, many cases of severe cholera were associated with eating specific cooked foods that could support bacterial growth after contamination of these foods with V. cholerae within the household. Epidemic control efforts should include identification of high-risk foods and promotion of simple changes in food handling behaviors to lower the risk of foodborne transmission.