This work is designed to investigate the factors controlling survival of pathogenic bacteria and certain fungi on human skin. We have shown that skin surface lipids are antimicrobial against certain pathogenic bacteria and fungi. We delineated populations of men in terms of persistence or inhibition of S. aureus applied to their skin. On this basis, this population is delineated as "persisters" and "inhibitors." We found a direct correlation between the quantitative reduction of experimentally inoculated S. aureus on the skin (in vivo) and the degree of their inhibition in vitro by acetone extracts of skin. The microbial flora of dermatitic skin is strikingly different from the normal skin biota. The carriage rate of S. aureus on dermatitic skin is 93%. Skin lipids from normal skin and dermatitic skin will be extracted with acetone and fractionated. Both quantitative and qualitative analysis of lipid will be tested for antimicrobial activity. These fractions will be characterized chemically. The isolation and successful identification of these fractions will be useful in investigating the effectiveness of these antimicrobial agents in the prevention of skin infections.