Sera from patients with pemphigus, other bullous dermatoses, and various control groups were examined to determine whether paramyxoviruses, particularly SV5 and DU, could be isolated. Indirect immunofluorescent tests and virus neutralization tests were employed to determine the incidence of SV5 virus antibody in sera from patients with various dermatoses, and to determine whether antibody to SV5 was related to the antiepithelial antibody associated with pemphigus. The frequency of antibody to SV5 (9%) and DU (11%) virus in sera from patients with pemphigus was not higher than the frequency of antibodies to SV5 (14%) and DU (17%) in sera of various control groups. The absence of antibodies to SV5 and DU virus in sera from most patients with pemphigus, the absence of intercellular antiepithelial antibody in sera from dogs and most humans with antibody to SV5 and DU virus, and the absence of correlation of titers in a patient with both types of antibody indicate that SV5 antibody is not functionally related to 'pemphigus antibody'. In addition, no SV5, DU, or other hemadsorbing paramyxovirus was isolated from sera of patients with pemphigus. Isolation from blister fluid was not attempted. Infection with SV5, DU, or similar paramyxovirus is probably not usually, if at all, related to the etiology of non Brazilian pemphigus.