Recent studies have demonstrated that the normal human testes, colon, and liver contain a substance that resembles hCG. To extend these findings, we examined aqueous extracts of a variety of normal human tissues for the presence of this material. The beta-hCG RIA, rat Leydig cell radioreceptor assay, and a newly developed, highly specific hCG RIA were used to measure hCG activity in a serial dilutions of the extracts. Detectable concentrations of the hCG-like material were found in 146 of the 149 individual tissue samples studied. Parallelism was noted between the hCG standard and serial dilutions of extracts of testis, ovary, pituitary, lung, liver, kidney, spleen, stomach, placenta, and some small intestinal tissue samples in the beta-hCG RIA, radioreceptor assay, and the highly specific hCG RIA. An absence of parallelism was found between extracts of nonpituitary tissues and LH in the beta-LH RIA. Pancreatic extracts altered the [125I]hCG used as the labeled ligand in these assays, which led to spurious results. Chromatography of the extracts on Concanavalin A-Sepharose columns revealed that the hCG-like materials from different tissues varied widely in their adsorbtion to Concanavalin A, possibly reflecting differences in their carbohydrate contents. These results indicate that an hCG-like substance is widely distributed throughout normal human tissues and further supports the concept that the fetal genome responsible for hCG production is not completely suppressed in adult tissues.