OBJECTIVE: To evaluate the parameters of oxidative and antioxidative systems in laryngeal carcinoma for their effects on pathogenesis. METHODS: Blood and plasma samples from 30 patients with laryngeal carcinoma were compared with 15 smokers who were otherwise healthy. The tumour tissue samples of the 30 patients were compared with the adjacent non-tumour-bearing mucosal tissue in which carcinoma was ruled out histologically. Although malondialdehyde was used as the main indicator of oxidative stress, superoxide dismutase, glutathione, and catalase activities were accepted as indicators of the antioxidative defense mechanism. RESULTS: Malondialdehyde was significantly higher in the plasma and blood of patients when compared with those of the control group. Glutathione, superoxide dismutase, and catalase activity levels were measured in blood, and these parameters were significantly higher in the control group (p < .001). All results were found to be statistically significant (p < .001). The malondialdehyde level was also found to be significantly higher (p < .01) in the tumour tissue sample. Among the parameters of the tissue antioxidative defense mechanism, superoxide dismutase levels were determined to be significantly higher (p < .001) in the tumour when compared with the levels in adjacent healthy tissue. However, there was no statistically significant difference between the glutathione and catalase activities of the tumour and non-tumour-bearing tissues (p > .05). CONCLUSION: Although the parameters of the oxidative system appear to increase, the antioxidative variants seem to be reduced in laryngeal carcinoma, with one exception: superoxide dismutase has been found in higher amounts in tumour tissue. These results may reflect the effect of oxidative stress in the pathogenesis of laryngeal carcinoma.