Summary Our data tend to confirm the observations of Livingston et al. (1) that a microorganism(s) isolated from the urine of cancer patients is capable of producing a human chorionic gonadotrophinlike substance. Chromatographic properties as well as immunologic and receptor assay techniques offer strong evidence for this similarity. We are indebted to Dr. K. Sundaram for his examination of the extracts for in vitro gonadotropic activity, and to Drs. M. Goore and N. Starkovsky for their aid in performing the radioimmunoassay and radioreceptor assay. Also, to Dr. Livingston for supplying us with cultures of the organism as well as samples of her isolates.