Serum and urine levels of tumour necrosis factor (TNF) which is a lymphokine was measured in patients with genitourinary cancer (either prostatic, bladder or testicular carcinoma) in order to find out whether there were elevated levels of TNF in those patients and if it was related to disease status. Although the preliminary results are not conclusive, further research on TNF may prove this immunoprotein to be a potential diagnostic and therapeutic agent.