The U.S. Army recently mandated that soldiers undergo glucose-6-phosphate dehydrogenase (G6PD) testing before deployment to malarious regions. We retrospectively characterize the presence and degree of G6PD deficiency in U.S. military personnel by sex, self-reported ethnicity, and World Health Organization deficiency classification through test results obtained October 1, 2004 through January 17, 2005. Data were available for 63,302 (54,874 males and 8,428 females) subjects; 2.5% of males and 1.6% of females were deficient, with most having only moderate enzyme deficiency. African American males (12.2%) and females (4.1%), along with Asian males (4.3%), had the highest rates of G6PD deficiency. Most males were found to have class III variants while most females were class IV variants. The most severely deficient were Asian males (class II). These results suggest that universal screening for G6PD deficiency is clinically warranted, and particularly essential for those male service members who self-report ethnicity as African American, Asian, or Hispanic.