We investigated the impact of a customized alcohol-based instant hand sanitizer hand-hygiene regimen in an Army basic training setting. The entire population at the U.S. Army Field Artillery Training Center, Fort Sill, Oklahoma, participated in the 13-week prospective cohort study between January 18, 2005 and April 18, 2005. Two training battalions were randomly assigned to the control group, one to the primary intervention group (customized Purell Instant Hand Sanitizer regimen, education, reinforcement) and one to the secondary intervention group (customized Purell Instant Hand Sanitizer regimen). When compared to the control group, intervention groups experienced 40% less respiratory illness (p < 0.001), 48% less gastrointestinal illness (p < 0.02), 44% less lost training time (p < 0.001), and 31% fewer health care encounters (p < 0.001). These findings suggest that this intervention is capable of significantly reducing illness in this setting and has the potential to help reduce absenteeism in the military workforce as a whole.