Urokinase plasminogen activation system can play an important role in the appearance and progression of many cancers. Urokinase-type plasminogen activator (uPA) is implicated in the control of cell adhesion and invasion, and is regarded as a strong prognostic marker in colorectal cancer. A C-->T substitution (the C/T polymorphism) in the nucleotide sequence encoding the kringle structure of uPA results in an alteration from proline to leucine at position 121. This substitution may be directly or indirectly involved in the decreased affinity for uPA substrates. In the present work the distribution of genotypes and frequencies of alleles of the C/T polymorphism were investigated. Tumour tissues and distal mucosa samples were obtained from 40 patients with colorectal cancer. Blood samples from sex and age matched healthy individuals served as control. The C/T polymorphism was determined by PCR amplification using the allele specific primers. No differences between genotypes of the C/T polymorphism in cancer tissue and distant mucosa of each patient were found. The distributions of the genotypes in both patients and control differed significantly (p < 0.05) from that predicted by the Hardy-Weinberg distribution. A distinct preference of heterozygotes (70% - patients, 65% - controls) was observed in both patients and controls. Additionally, there were no differences in the frequencies of the C and T alleles in both groups. The C/T polymorphism of the uPA gene may not be linked with colorectal cancer.