The effect of hydration on Staphylococcus epidermidis, the predominant resident bacterial flora, was studied on skin affected by leprosy and known to have impaired sweating. Normal areas served as control. Significantly higher bacterial counts were observed in affected areas compared with normal-looking skin in 16/19 of the patients. Artificial application of Staph. epidermidis on leprosy-affected and unaffected areas, however, showed equivocal results, as in only 50% of the patients were higher counts obtained in affected compared with unaffected sites. The possible responsible factors for the present observation are discussed.