Betacellulin (BTC) belongs to the EGF family, whose members play important roles in skin morphogenesis, homeostasis, and repair. However, the role of BTC in skin biology is still unknown. We employed transgenic mice overexpressing BTC ubiquitously to study its role in skin physiology. Immunohistochemistry revealed increased levels of BTC especially in the hair follicles and in the epidermis of transgenic animals. Expression of key markers of epithelial differentiation was unaltered, but keratinocyte proliferation was significantly increased. At post-natal day 1 (P1), transgenic mice displayed a significant retardation of hair follicle morphogenesis. At P17, when most follicles in control mice had initiated hair follicle cycling and had already entered into their first late catagen or telogen phase, all follicles of transgenic mice were still at the mid- to late catagen phases, indicating retarded initiation of hair follicle cycling. Healing of full-thickness excisional wounds and bursting strength of incisional wounds were similar in control and transgenic mice. However, an increase in the area covered by blood vessels at the wound site was detected in transgenic animals. These results provide evidence for a role of BTC in the regulation of epidermal homeostasis, hair follicle morphogenesis and cycling, and wound angiogenesis. © 2007 The Society for Investigative Dermatology.