This study attempts to correlate the frequency of infection by Candida with the following immunological factors presented in cancer patients undergoing chemotherapy: neutrophil number; level of exogenous myeloperoxidase (MPO); cytokines IL-12, IL-10, TNF-alpha and IFN-gamma. A total of 31 serum and blood samples were tested for MPO and cytokines concentrations by using the ELISA technique. The level of cytokines and MPO was measured in serum samples and whole blood cell culture (WBC) supernates. We observed that: 1) MPO deficiency seems to be an important risk factor for invasive candidiasis independently of the neutrophil count; 2) the levels of cytokines in serum showed disturbances in cancer-patient group; 3) in vitro production of TNF-alpha, IFN-gamma and IL-10 by WBC is stimulated in cancer patients and to various degrees may be connected with previous Candida colonization or infection. In addition, production of IL-12 is decreased in cancer patients, and Candida spp. Occurrence may have significant influence on its blood concentration.