OBJECTIVE Crohn's disease (CD) and ulcerative colitis (UC) are chronic inflammatory diseases of the bowel, the causes of which are not fully known. Ethnic differences in disease prevalence, familial aggregation of the disease and studies of twins provide the most important evidence to suggest that genetic factors play a role in the pathogenesis of inflammatory bowel disease (IBD). The aim of this study was to examine the allelic polymorphisms that can determine the immune response levels in tumor necrosis factor alpha (TNFalpha), interleukin-1beta (IL-1B), interleukin-1 receptor antagonist ( IL-1RN) and interleukin-10 (IL-10) genes and to investigate their roles in the inflammatory pathway in IBD. METHODS The study included 120 patients with UC and 70 patients with CD who were diagnosed either endoscopically or histopathologically. The control group comprised 105 healthy individuals who stated that they had never had any bowel disease during their life span. The polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) method for polymorphisms in the TNFalpha gene at positions -308 and -238, the IL-10 gene at positions -1082 and -627, the IL-1B gene at -511 regions and the variable number of tandem repeat (VNTR) method for polymorphism in the intron 2 of the IL-1RN gene were performed. The results were analyzed on agarose gel electrophoresis. RESULTS No significant differences were found in the allele and genotype frequencies of the polymorphisms in the IL-1B, IL10, TNFalpha and IL-1RN genes between the patients with UC and CD and controls. CONCLUSIONS The results suggest that these polymorphisms were not important risk factors in the susceptibility to IBD in Turkish patients.