Using complement immunofluorescence, the capability of complement fixation by bound antibodies in pemphigus lesional skin was compared with circulating intercellular antibodies of complement-fixing type in the same patient. Five lesional skin samples from 6 patients, containing bound IgG, gave positive binding of complement (C3) supplied from fresh guinea pig serum, while only one serum sample showed complement-fixing pemphigus antibodies in the circulation. These results support the view that complement-fixing pemphigus antibodies are rapidly localized to the skin and play a role on the production of acantholysis.