Bacterial species, which occur on the breast skin surface of adult (1 year old) white leghorn fowl with intact uropygial gland, were identified as : Staphylococcus epidermidis, Sarcina lutea, Streptomyces sp. and a facultative diphtheroid belonging to the genus Corynebacterium; S. epidermidis being the most predominant one. Two species of bacteria, namely, Staphylococcus aureus and Proteus sp. were shown to colonize the skin surface after 60 days of captivity. Extirpation of uropygial gland caused severe depletion of population of S. epidermidis, Streptomyces sp. and diphtheroid. The effect was more conspicuous after 60 days compared to that after 30 days of the gland removal. On the skin surface of glandless fowls the population of S. aureus increased significantly and a new form identified as anthracoid bacillus became the most predominant species after 60 days. Addition of total lipids from the free-flowing fowl uropygial secretion, as 0.2% suspension, to trypticase soya broth cultures of individual bacteria of fowl skin surface encouraged strongly the growth of S. epidermidis, Streptomyces sp. and Proteus sp. but suppressed the population of the anthracoid. When identical amount of diester wax or wax alcohol of the secretion was supplemented to the culture, more or less similar result was obtained. Wax alcohol also had a mild inhibitory effect on Streptomyces sp. Wax acids, added to the culture (0.2%) suppressed population of all the bacterial forms except Proteus sp., while the hydrocarbon fraction, which also contained some amount of squalene, produce an opposite effect.