Serum selenium levels were determined by fluorometric procedure in 37 patients of both sexes suffering from colorectal cancer. The diagnosis was verified with histopathological examination during surgical treatment. The values found were 46.8 +/- 11.2 micrograms/L. The control group consisted of 230 healthy persons from the same environment as the group of patients. The values found were 64.2 +/- 11.5 micrograms/L. The results of this study are compared with the results of the other research groups analyzing the level of selenium in colorectal cancer.