In this review we have tried to argue that the evidence indicating that the LH/CG receptor is composed of a single polypeptide is stronger than the evidence indicating that the LH/CG receptor is a more complex structure composed of several subunits. Clearly, however, this issue has not been resolved and probably will not be resolved by performing additional experiments similar to those summarized here. It is our opinion that this issue will be resolved only by 1) reconstitution experiments in which the ability of the purified LH/CG receptor to bind hCG and activate adenylyl cyclase activity is tested; and/or 2) isolation and expression of a full length complementary DNA (cDNA) for the LH/CG receptor and the demonstration of hCG binding and adenylyl cyclase activation by the expressed receptor. Similar experiments will also clarify the proposed structures for the FSH and TSH receptors. As the second decade of work on the LH/CG receptor draws to an end it appears that these experiments are now possible, and hopefully a resolution of the existing controversy will be forthcoming in the near future.