Nerve growth factor (NGF), a well-characterized neurotrophic factor, induces an increase in the number of mast cells (MCs) in the peripheral tissues of developing rats, as well as histamine release in fully differentiated MCs. Since MCs increase in the dermis of patients with early systemic sclerosis (SSc), we examined the distribution of NGF in the skin of patients affected by SSc. Immunohistochemical studies showed that NGF distribution was more intense in the dermis of patients with SSc than in the skin of controls. A possible correlation between MCs and NGF in disease activity is hypothesized.