A combination of 2 or 3 tumor markers was determined in the serum of 478 patients with malignant tumors. In 195 out of 213 patients with differentiated thyroid cancer and without relapse or metastases, the Tg concentration has undetectable. In 9 patients with nonfunctioning thyroid metastases the Tg level was correlated with the progress of the disease or the success of the treatment. In 114 patients with gastrointestinal cancer CA 19-9, TPA and IAP were measured simultaneously. The highest discrepancies between patients with relapse or metastases (increased values in 1/2 of patients) and patients without relapse or metastases (increased values in 1/4 of patients) were given by CA 19-9. In the serum of 90 patients with breast cancer increased CA 15-3 values were found in 2/3 of patients with relapse or metastases and in 1/4 of patients without signs of tumor. A combination of universal tumor markers TPA and IAP had no value in monitoring 26 patients with melanoma.