Adipose tissue encircles the lower portion of anagen hair follicles and may regulate hair cycle progression. As leptin is a major adipokine, its level of expression from the dermal white adipose tissue during hair cycle progression was studied. The result shows that leptin level is differentially expressed during hair cycle, the lowest in early anagen phase, upregulated in late anagen phase and the highest in the telogen phase. On the other hand, leptin receptor is detected in keratin 15-positive hair bulge epithelium of both anagen- and telogen-phase hair follicles of mice pelage and vibrissa hair, and hair from human scalp. Leptin contributes to adipocyte-mediated growth inhibition of anagen-phase vibrissa hair as demonstrated in organ culture and coculture system. Our data suggest that leptin of dermal white adipose tissue might regulate hair growth and, therefore, hair cycle progression via leptin receptor on the hair follicle epithelium.