Diarrhea remains a potential cause of compromised military effectiveness. To assess diarrhea rates and mission impact in operations in Iraq and Afghanistan, a survey was administered to soldiers participating in the "Rest and Recuperation" program in Doha, Qatar. Between October and December 2003, 2,389 volunteers completed a questionnaire designed to assess the occurrence and impact of diarrhea. The median length of deployment was 7.2 months, 70% reported at least one episode, and 56% had multiple episodes of diarrhea. Overall, 43% reported decreased job performance for a median of 2 days, and 17% reported being on bed rest for a median of 2 days. While this survey showed high rates of diarrhea associated with decreased operational effectiveness, the results are consistent with prior military operations in this region. Further research is needed to develop better methods for illness prevention and its minimization on operational impact.