We studied 3 recent cases of paraneoplastic pemphigus (PNP) in detail. Two patients died despite concerted management efforts. One patient received no treatment after the appearance of PNP and recovered completely from both PNP and lymphoma. Multiple serum studies of these 3 patients plus 9 other proven PNP cases revealed that 8 of 9 fatal PNP cases (referred to here as "group A") had distinctive cell surface antibodies detected by complement indirect immunofluorescent (CIIF) tests on monkey esophagus sections. By contrast, none of the sera from 3 patients with PNP who experienced long-term survival (referred to here as "group B") and none of 20 pemphigus vulgaris or 10 pemphigus foliaceus control sera revealed similar beaded cell surface CIIF reaction patterns, a difference that is statistically significant (P <.0001). Cell surface CIIF reaction patterns of group A PNP antibodies resemble the pattern of pemphigus antibody reactions in indirect immunofluorescent tests on the same substrate; however, the latter tend to be thinner and more linear, whereas the cell surface CIIF pattern tends to be more beaded, suggesting possible desmosomal reactions. We believe this test is useful in identifying an aggressive group A form of PNP.