Hair follicles in the telogen stage of the hair cycle were induced into anagen phase after the skin of the South American opossum, Monodelphis domestica, was exposed to levels of ultraviolet B radiation (280 to 320 nm), which induced desquamation. Post-ultraviolet B exposure to long-wavelength radiation (320 to 400 nm, ultraviolet A) suppressed the induction of edema and desquamation and the induction of hair growth. Hair growth induction was also observed in skin damaged either by mechanical abrasion or by exposure to methoxsalen and ultraviolet A