In the sera of 30 neoplasm patients without metastases, the average IgG level was higher than in the control group (CG) (18.16 + 5.10 versus 12.62 + 2.14 g/l or 12.22 + 2.14 after excluding an out-lier). Average concentrations of CIC, IgM, C1i, C3c and C4 did not statistically differ between the groups. Dividing the patients' group into breast or ovary cancer (BC), melanoma (M), digestive tract cancer (DT) and other neoplasms (ON) subgroups revealed that the IgG increase did not apply to the BC group. Relatively decreased CIC concentrations in the BC and DT group and an increased C1i in the DT group were found. Several diversities detected in the humoral immunity indices' distributions and correlations suggest activation of different mechanisms depending on the neoplasm types.