Forty biopsies from 22 patients undergoing tissue expansion were examined histologically. Expanded skin demonstrated a generally unconspicious morphology of the epidermis, dermis and subcutis. Adnexal organs of the skin were preserved. Mean epidermal thickness was increased to 710 +/- 240 microns compared to 624 +/- 215 microns in the controls. The tissue expanders were bordered by a richly vascularized connective tissue capsule with a very variable mean thickness of 795 +/- 712 microns. These histologic findings in human tissues support experimental evidence for a real increase in tissue by expansion.