Mammalian hairs are formed by differentiation and keratinization of cells produced in the epidermal matrix (Figs 3, 4). Using the rodent vibrissa follicle as a model¹, transplantation studies have shown that the dermal papilla, a discrete population of specialized fibroblasts, is of prime importance in the growth of hair^2,3. Papillae induce hair growth when implanted into follicles^4,5 and can interact with skin epidermis to form new hair follicles⁶. When grown in culture, papilla cells display singular morphological and behavioural characteristics compared with connective tissue cells from other skin sources^7,8. We report here that serially cultured adult papilla cells can induce the growth of hair when implanted into follicles which otherwise would not grow hairs. This finding presents an opportunity to characterize properties distinguishing the papilla cell population from other skin fibroblasts, and, more specifically, those which control hair growth. The eventual application of this work to human hair replacement techniques can also be envisaged.