International travel projections suggest that physicians will be increasingly involved in counseling their traveling patients on the prevention of health hazards. A mail survey of 121 returning international travelers indicated that their leading problems involved drinking water (odds ratio [OR], 19.4; 95% confidence interval [CI], 9.6 to 39.1), sanitation (OR, 13.8; 95% CI, 6.9 to 27.5), jet lag (OR, 12.4; 95% CI, 6.2 to 24.6), and food (OR, 9.5; 95% CI, 4.8 to 18.8). Medication for treatment of travelers' diarrhea and countermeasures for jet lag were not significantly associated with better outcomes. Compliance with malaria chemoprophylaxis was greater than previously reported.