In renal carcinoma, the inappropriate, unscheduled, or aberrant production of hormones and other serologic markers and the resulting clinical or biochemical syndromes are unique manifestations of this tumor. The elaboration of biologically active factors by renal adenocarcinoma may add a metabolic burden to an already compromised host, and thus affect therapy and prognosis; they should be considered before ascribing symptoms to metastasis or dissemination. Similarly it has been suggested that the elaboration of biologically-inactive peptides and proteins is a very common concomitant of neoplasia and the identification of such factors may facilitate earlier diagnosis and novel therapies in patients with renal carcinoma.