We have previously demonstrated that pemphigus antibodies will fix complement to organ and tissue cultured epidermal cells in vitro. In the present study, we sought to determine the role complement plays in the detachment of cultured murine epidermal cells by pemphigus antibody. Forty-eight hour cultivated epidermal monolayers from neonatal BALB/c mice were treated with purified IgG fractions of pemphigus sera in the presence or absence of complement. In the absence of complement, pemphigus IgG produced slight cell detachment when compared to an identical amount of normal IgG. When cells were maintained in media with pemphigus IgG plus complement for 48 h, the cell detachment was significantly higher than that obtained with pemphigus IgG alone, or with normal IgG plus complement. Heat inactivation or Clq depletion of the complement source resulted in complete inhibition of cell detachment. When pemphigus F(ab')2 plus complement was used instead of whole pemphigus IgG plus complement, the cell detachment rate was again lowered significantly. Both pemphigus IgG and the complement source were depleted of plasminogen by passage over a lysine-Sepharose 4B column, and tested for their effects on cell detachment depleted of plasminogen. Depletion of plasminogen failed to inhibit cell detachment induced by pemphigus IgG and complement. These results suggest that complement activated by pemphigus antibody binding to the epidermal cell surface induces epidermal cell detachment and would argue against the plasminogen-plasmin system as the sole cause of cell detachment in pemphigus.