An outbreak of hepatitis A infections occurred among patrons of an Ohio restaurant. The restaurant's food workers were tested for hepatitis A; there was no evidence that a food handler could have contaminated the food with hepatitis A virus. A case-control study determined that foods containing green onions were associated with illness. A traceback on the green onions indicated that they had originated either from Mexico or California. The contaminated green onions were likely to have been distributed widely throughout the USA, yet no other cases of green onion–associated hepatitis A were identified.