Different conceptions exist regarding the epidemiology and prognosis of liposarcoma, and several classification systems are in use. We analyzed a population-based, 25-year series of 43 patients with liposarcoma of the extremity or trunk wall. Follow-up was complete. The annual incidence was 0.12/10(5). The thigh was the most common location. One of 6 tumors was subcutaneous. Deep-seated tumors were larger than s.c. tumors. Among the 42 surgically treated patients, grade II (4-grade scale) was the most common malignancy grade. Four tumors were well-differentiated, 24 were predominantly myxoid, 4 predominantly round-cell, and 10 were predominantly of pleomorphic type. The 5-year metastasis-free survival rate was 69%. By univariate analysis increasing malignancy grade, tumor necrosis, vascular invasion, mitotic count, subtype other than well-differentiated, and high cellularity were prognostic for metastatic disease. However, in the multivariate analysis only tumor necrosis was an independent risk factor. Tumor necrosis should be considered when prognosis of liposarcoma of the extremity and trunk wall is evaluated.