Food is the primary vehicle of transmission for traveler's diarrhea. We evaluated coliform contamination of vegetables from popular restaurants in Guadalajara, Mexico, and Houston, Texas. Contamination of vegetables in Guadalajara restaurants was widespread. Prevention of traveler's diarrhea by avoidance of "high-risk" foods may be unsuccessful, because contamination of foods may occur regardless of how they are prepared. © 2008 by the Infectious Diseases Society of America. All rights reserved.