The aim of this study is to evaluate the effect of ultraviolet B (WB) on arsenic-induced Bowen's disease. Four patients were irradiated with 750 mJ/cm(2) of UVB and biopsies were performed before treatment and 2 weeks later. Immunohistochemical stains of p53 and Ki-67 were compared by the labelled-streptavidin method before and after the UVB treatment. We found that the number of p53 and Ki-67 positive cells after the UVB treatment were significantly fewer than those of non-UVB-treated specimens. These results suggest that the UVB inhibitory effect in Bowen's disease needs further studies to clarify its value in potentially retarding the progression of the hyperproliferative status in overt skin cancer on a molecular basis. (C) Munksgaard 1997.