Conclusions. It can be concluded that these changes are related to damage at the DNA level or to the inhibitory effects of tumor promoters. Increases in GSH-Px activities may be related to the independence of this enzyme from the suppressive effects of tumor promoters. This study and others in the literature show that it is not possible to generalize the activities of SOD and GSH-Px in cancer. Objective. There has been growing interest in the role of free radicals as a cause of cancer. It has been suggested that an increase in activated forms of oxygen in cells due to overproduction and/or the inability to destroy them may lead to severe damage of cell structures. As a result of these changes, some chromosomal aberrations and carcinogenesis may develop. Superoxide dismutase ( SOD) and glutathione peroxidase (GSH-Px) are two important antioxidant enzymes involved in enzymatic antioxidant defense mechanisms. To our knowledge there have been no previous studies in the literature investigating the activities of SOD and GSH-Px in laryngeal cancer. Material and methods. The study subjects comprised 10 male patients (age range 43-76 years) with laryngeal carcinoma and 10 healthy controls ( 4 males, 6 females; age range 40-69 years) with intraoral hyperplastic fibrous tissue. Homogenate SOD and GSH-Px activities were measured using commercially available kits. Results. GSH-Px levels were significantly increased in the cancerous tissues compared with cancer-free adjacent tissues and fibrous hyperplasia tissues (p < 0.05), whereas there was no significant difference between SOD activities (p > 0.05). There was also no significant difference between GSH-Px activity in cancer-free adjacent tissues and fibrous hyperplasia tissues (p > 0.05).