In order to look for a new culture system suitable for investigating on melanocyte biology, in-vitro experiments have been carried out on pigmented basal cell carcinoma, pigmented seborrhoeic keratosis and melanocytic nevus. Melanocytes cultured from pigmented basal cell carcinoma and pigmented seborrheic keratosis are dendritic and DOPA positive. These cells can be considered similar to those of normal skin. Pigmented cells cultured from nevi are quite different. They are spindle-shaped and only to a little extent are DOPA positive. These findings suggest that nevus cells could be non mature melanocytes stopped at an intermediate stage of differentiation.