The aim of the study was to analyze serum tumor necrosis factor alpha (TNF-alpha) levels in patients with different neoplasm types qualified for surgical treatment and to evaluate their possible correlations with circulating immune complexes (CIC), IgG, IgM, and the complement (C) compounds: C1 inhibitor (C1i), C3c and C4 levels. Studies were performed in sera from 30 neoplasm patients before surgical treatment and in 10 persons from a control group (CG) with no malignancy. Serum TNF-alpha levels were measured with the Cytogen ELISA kit. Average TNF-alpha levels measured in neoplastic patient groups qualified for surgical treatment were not significantly different from the average TNF-alpha level in the CG group.