We report the isolation of clones from a human thymus cDNA library that code for the alpha 3 subunit of a neuronal acetylcholine receptor (AcChR). The clones hybridize to one major 3.0-kb mRNA thymic species and four minor ones of approximately 2.3, 4.0, 5.0, and 6.5 kb, but they do not hybridize to human muscle mRNA. These clones may be of value in defining the cholinergic thymic makeup and the putative role that a thymic AcChR may have in the triggering and/or maintenance of an anti-AcChR response in the autoimmune condition myasthenia gravis.