We report for the first time the successful maintenance and growth of human hair follicles in vitro. Human anagen hair follicles were isolated by microdissection from human scalp skin. Isolation of the hair follicles was achieved by cutting the follicle at the dermo-subcutaneous fat interface using a scalpel blade. Intact hair follicles were then removed from the fat using watchmakers' forceps. Isolated hair follicles maintained free-floating in supplemented Williams E medium in individual wells of 24-well multiwell plates showed a significant increase in length over 4 days. The increase in length was seen to be attributed to the production of a keratinised hair shaft, and was not associated with the loss of hair follicle morphology. [methyl-3H]thymidine autoradiography confirmed that in vitro the in vivo pattern of DNA synthesis was maintained; furthermore, [35S]methionine labelling of keratins showed that their patterns of synthesis did not change with maintenance. The importance of this model to hair follicle biology is further demonstrated by the observations that TGF-beta 1 has a negative growth-regulatory effect on hair follicles in vitro and that EGF mimics the in vivo depilatory effects that have been reported in sheep and mice.