It has previously been shown that multiple messenger RNA (mRNA) species can be identified in gonadal tissues by probes specific for the LH/CG receptor. Here we show that the sizes and relative abundancies of gonadal LH/CG receptor transcripts are quite variable between such closely related species as rat and mouse. These patterns of LH/CG receptor mRNAs are yet different from that observed in human embryonic kidney 293 cells that have been transfected with a cDNA encoding for the rat luteal LH/CG receptor. In spite of the diversity in the number and sizes of LH/CG receptor mRNA transcripts, however, our data also show that the size of the cell surface receptor expressed in these three cells/tissues is identical. We further show that the most abundant LH/CG receptor mRNA present in MA-10 cells, a clonal strain of cultured Leydig tumor cells, is a 1.2 kilobase transcript which encodes for a truncated version of the LH/CG receptor corresponding to the extracellular hormone-binding domain. It does not appear, however, that this transcript is translated into a functional protein.