Lymphomatoid papulosis (LyP) is a disorder which generally runs a benign course, but can sometimes be associated with a malignant lymphoma. Information about the prognosis of these LyP-associated lymphomas is, however, fragmentary. In this study, the clinical data of 50 LyP-associated malignant lymphomas, including 11 patients of our own group and 39 reported in the literature, are evaluated. Three main groups of LyP-associated malignant lymphomas could be distinguished: cases associated with mycosis fungoides (19/50 cases). Hodgkin's disease (12/50 cases) and (CD30+) large-cell lymphomas (16/50). The results of this study demonstrate that patients with mycosis fungoides. Hodgkin's disease, and (CD30+) large-cell lymphomas limited to the skin have a favourable prognosis. However, the prognosis of patients developing a systemic (CD30+) large-cell lymphoma proved generally poor. The results of this study also indicate that the risk of an individual LyP patient developing systemic lymphoma is less than 5%.