Subcutaneous adipose tissue was examined in 77 patients with breast cancer, 61 patients with lung cancer and in a control group of 23 male and 27 female with non-tumor pathology; the weight and age of controls matched those of cancer patients. The obesity in breast cancer patients was of the hypertrophic type, and of combined type (hypertrophic-hyperplastic) in patients who were more than 50% overweight. The increased level of adipose tissue in lung cancer patients was mostly due to the larger size of adipocytes. The concentration of unsaturated fatty acids in adipose tissue in breast cancer patients was in direct correlation with the level of this tissue and adipocyte size, while, in lung cancer group, this correlation was reversed. There was no inverse correlation between the size and c-AMP level of adipocytes in both cancer groups. Resistance to the inhibitory effect of glucose on lipolysis occurring in adipose tissue was more frequent in cancer patients than in controls. Antilipolytic effect of insulin in subcutaneous adipose tissue of breast cancer patients was less pronounced than in lung cancer group. Liposynthetic activity in adipose tissue was identical in all study groups. Lipolytic activity in adipose tissue was enhanced in both cancer groups, but in the breast cancer group it was in direct correlation with overweight, while in lung cancer patients--with the degree of tumor progression.