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Background: The purpose of the study was to genotype four polymorphisms in CYP3A5 (CYP3A5*2, CYP3A5*3, CYP3A5*3B, and CYP3A5*6) for a possible association between individual genetic variations and susceptibility to colorectal cancer. Another point of interest was to conduct a comprehensive analysis in tumor and normal intestine tissue from the same patient, searching for somatic hotspots., Material and Methods: In our study, 146 Bulgarian patients with sporadic colorectal cancer and 160 healthy volunteers were enrolled. CYP3A5 polymorphisms were identified using rapid-cycle real-time amplification with allele-specific probes and subsequent melting curve analysis on a LightCycler., Results: The allele frequencies were comparable in both groups: frequency of CYP3A5*2 = 0.3% in patients vs. 0.6% in controls; frequency of CYP3A5*3 = 90.8% in patients vs. 93.1% in controls; in both groups no CYP3A5*3B and CYP3A5*6 variants were detected (p > 0.05). No difference was observed between genotype frequencies in tumor and surrounding normal tissues of 80 patients., Conclusions: The CYP3A5 variants are unlikely to have an important functional significance in patients with colorectal cancer. The studied CYP3A5 loci do not seem to be hotspots for somatic mutation. DNA from archived tumor tissues is a valid alternative to the use of leukocyte DNA for genotyping of these polymorphisms.