Within the group of primary cutaneous T-cell lymphomas (CTCLs), mycosis fungoides (MF), Sézary's syndrome (SS), and CD30-positive lymphomas have been delineated as clinicopathological entities. Primary CTCLs that do not belong to one of these entities represent a heterogeneous and ill-defined group of neoplasms. This paper describes the clinical and histological features of 35 of such cases. The object of this study was to define prognostic parameters for this group of primary CTCLs. Using a slightly modified version of the updated Kiel classification, a subdivision was made into CTCL, pleomorphic, small cell type (n = 3); pleomorphic, medium-sized cell type (n = 6); pleomorphic, large cell type (n = 18); and immunoblastic lymphomas (n = 8). Altogether, these lymphomas had a poor prognosis with estimated 2- and 4-year survival rates of 53 and 22 percent, respectively. Patients with pleomorphic, small and medium-sized cell lymphomas (n = 9) proved to have a significantly better survival than those with pleomorphic, large cell lymphomas (P = 0.032) and immunoblastic lymphomas (P = 0.008). Primary cutaneous immunoblastic lymphomas had the worst prognosis with an estimated 2-year survival rate of 14 percent. Other parameters including age (P = 0.345), sex (P = 0.662), extent of skin lesions at presentation (P = 0.0854), and mode of initial treatment (P = 0.609) had no significant effect on the survival time. The results of this study suggest that primary CTCLs other than classical MF, SS, and CD30-positive lymphomas have a poor prognosis in most cases, and that the current classification may be a useful means of predicting the clinical behaviour in these lymphomas.