The relationship between herpes simplex virus (HSV) and erythema multiforme (EM) has been well described. Many authors contend that EM (excluding Stevens-Johnson syndrome and toxic epidermal necrolysis) occurs almost exclusively as a response to HSV infection. During the past year, however, we have observed several cases of EM complicating severe Rhus allergic contact dermatitis. Although this association has been previously documented, the paucity of cases in the literature, along with our experience, suggests that this is an underreported phenomenon. We describe 4 of our cases.