Six double-blind, independently randomized studies evaluated the efficacy and safety of calcium mupirocin ointment in eliminating nasal carriage of Staphylococcus aureus among health care workers. Healthy volunteers with stable nasal carriage of S. aureus (n = 339) received either calcium mupirocin ointment (n = 170) or an identical placebo ointment (n = 169) intranasally for 5 days. Nasal carriage was eliminated 48-96 hours after completion of treatment in 130 (91%) of 143 evaluable volunteers receiving mupirocin but in only 8 (6%) of 142 evaluable volunteers receiving placebo. The 85% crude difference represents a 90% pooled (adjusted) estimate of the risk difference (95% confidence interval, 0.86-0.95) and a risk ratio of 16 (P < .0001). This effect of treatment with mupirocin was observed consistently (risk ratio, 8-32) in all six centers. In addition, 96 of the 130 mupirocin-treated volunteers and 1 of the 8 placebo-treated volunteers who were culture-negative at the end of therapy remained free of S. aureus 4 weeks after treatment. Adverse events in each treatment arm were mild and equally frequent. These data, consistent across six institutions, demonstrate that calcium mupirocin ointment administered intranasally for 5 days is safe and effective in eliminating stable nasal carriage of S. aureus.