Histopathology alone cannot predict the outcome of patients with CD30+ primary cutaneous lymphoproliferative disorders (CD30CLPD) and early mycosis fungoides (MF). To test the hypothesis that serum cytokines/cytokine receptors provide prognostic information in these disorders, we measured soluble CD30 (sCD30), sCD25, and selected cytokines in cell cultures and sera of 116 patients with CD30CLPD and 96 patients with early MF followed up to 20 years. Significant positive correlation was found between sCD30 levels and sCD25, CD40L, IL-6, and IL-8, suggesting that CD30+ neoplastic cells secrete these cytokines, but not Th2 cytokines. In vitro studies confirmed that sCD30, sCD25, IL-6, and IL-8 are secreted by CD30CLPD-derived cell lines. CD30CLPD patients with above normal sCD30 and sCD25 levels had worse overall and disease-related survivals, but only sCD30 retained significance in Cox models that included advanced age. High sCD30 also identified patients with worse survival in early MF. Increased IL-6 and IL-8 levels correlated with poor disease-related survival in CD30CLPD patients. We conclude that (1) neoplastic cells of some CD30CLPD patients do not resemble Th2 cells, and that (2) high serum sCD30, sCD25, IL-6, and perhaps IL-8 levels may provide prognostic information useful for patient management.