Nicotinic acetylcholine receptor (AChR) was purified from denervated and normal rabbit muscle using two affinity chromatography steps. Examination of the purified AChRs, radiolabeled with Na 125I, with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed identical patterns for both AChRs, consisting of 4 polypeptide bands with apparent M rs of 42, 44, 52 and 68 Kdaltons and a broad band in the 58 kdalton region. The sedimentation coefficient for both AChRs was 9 S, a value corresponding to the monomeric form of Torpedo AChR. The 42 Kdaltons subunit of denervated AChR was labeled by the affinity alkylating reagent [ 3H]4-(N-maleimido)phenyltrimethylammonium. Antiactin serum binds to the 44 kdalton polypeptide. Sera which had high titer against human AChR and veal AChR precipitated denervated AChR indicating a high degree of homology within mammalian AChRs.