Human dermal fibroblast and human epidermal keratinocyte survival was examined under various conditions in organ culture. Using cell recovery from organ-cultured tissue as the criterion, it was observed that no keratinocytes and few fibroblasts survived incubation for 10-12 days in serum-free basal medium containing a low level (0.15 mM) of extracellular Ca 2 § Increasing the extracellular Ca 2 § concentration to 1.4 mM or treating the tissue with 3 gM retinoic acid (RA) under low Ca 2+ conditions resulted in increased keratinocyte and fibroblast survival; the two treatments together were more effective than either treatment alone. The same treatments preserved fibroblast survival when pieces of isolated dermal tissue were incubated in organ culture and also supported fibroblast survival in monolayer culture. These findings indicate that recovery of keratinocytes and fibroblasts from skin after maintenance in organ culture provides a simple but definitive measure of the viability of the major cellular elements present in the tissue. These findings suggest that RA treatment enhances survival of both fibroblasts and keratinocytes and that these effects of RA can be seen at physiological Ca 2 § concentrations as well as at suboptimal levels of extracellular Ca 2+. Finally, these results indicate that the dermis is a direct target of RA.