Over the 33-day duration of the 1999 Haj in Saudi Arabia, we collected daily health status reports for 2070 Pakistani pilgrims over 13 years of age, 54% of whom had elected to receive influenza vaccine immediately before departing for the Haj. We calculated vaccine preventable outcome incidence as the difference in attack rates between vaccinated and unvaccinated persons. The incidences of vaccine preventable influenza-like illness (sore throat in combination with cough or fever of at least 38 degrees C), fever, and any symptom of upper respiratory infection were 22, 17, and 24 per 100 pilgrims per Haj. For every 100 persons who attended the Haj, 17 had a course of antibiotics and 23 had a course of nonprescription cold medication that was preventable with influenza vaccine use. Influenza leads to significant morbidity and medication use among Haj pilgrims. Vaccine against influenza should be considered for pilgrims before entry into Saudi Arabia.