Patients with a diagnosis of primary classic Kaposi's sarcoma (CKS) appear to be at a higher risk of multiple neoplasms. We analyzed a nation-wide series of 1,016 patients with a primary CKS occurring between 1961 and 1992 in the Jewish Israeli population to evaluate the risk of secondary neoplasms. The primary CKS and subsequent neoplasms were identified from the Israel Cancer Registry. All HIV-seropositive Kaposi's sarcoma cases were excluded. The expected number of second primary neoplasms was calculated after stratifying by age, origin and gender. Of the CKS patients, 61 developed a second neoplasm by the end of the study, similar to the expected number of 60.33 [standardized incidence ratio (SIR) of 1.01]. However, there was an excess of non-Hodgkin's lymphoma (NHL) (SIR = 3.94) and cutaneous malignant melanoma (SIR = 5.81), balanced by a deficit of lung cancers (none observed, 7 expected). We found high risk for migrants from Eastern Europe when compared with other migrants for both solid tumors [rate ratio (RR) = 3.01] and NHL (RR = 4.10). Patients with a diagnosis of primary CKS do not have an overall increased risk of new neoplasms later in life. However, an increased risk of NHL implies the presence of common risk factors for both NHL and CKS.