The aim of the study was an evaluation of changes in protein level and activity of SOD isoenzymes, and the participation of AP-1 and NF-kappaB in subsequent stages of colorectal cancer development. Studies were conducted on 65 colorectal cancers. Controls were unchanged colon regions. Activity of SOD isoenzymes, lipid peroxidation level (TBARS), and protein level of SOD1, SOD2, AP-1 and NF-kappaB were determined. We found that the protein level and activity of SOD isoenzymes and protein level of AP-1 and NF-kappaB change in subsequent stages of clinical advancement of colorectal cancer, according to UICC (I-IV), and in grades of tumor cells differentiation (G(1)-G(3)). These results indicate adaptation of colorectal cancer cells to oxidative stress, and show that the observed changes of SOD activity and protein level depend on gradual progression of colorectal cancer, and suggest an impairment of processes regulated by AP-1 and NF-kappaB which are critical for tumor progression (proliferation, differentiation and apoptosis).