A relationship was studied between generation of glucose-induced reactive oxygen species capable of causing damage to DNA (genotoxic or G-effect) and insulin secretion (endocrine or hormonal effect - H-effect) in primary menopausal patients with endomrnetrial carcinoma (EC) (32) or colonic cancer (CC) (16). The study group was compared with healthy menopausal women (25) and patients with an impaired glucose tolerance (IGT) (21). Besides, we examined 32 menopausal patients (CC--6 and EC--26) more than 12 months after surgery. The following basic patterns were established: (1) H-effect was reported in EC-1 and 1GT groups nmore often than in healthy peers and those with EC-2: (2) G-effect tended to prevail in CC patients and those with EC-2 and in patients with EC-1 twelve months after operation; (3) G-effect occurred more often in primary EC patients, particularly, those with EC-2 (71%) and IGT (58%) (as compared with CC patients (33%) and healthy females (p < or = 0.001). It is suggested that a comparison of the two effects might provide a criterion for use of relevant means of prevention of certain malignancies or correction of disorders in cancer patients following radical treatment.