Pressures generated by the pharyngeal constrictor muscles and proximal esophagus involve acetylcholine-induced muscle contractions. We hypothesized that the pharyngo-esophageal pressure gradient is related to choline acetyltransferase activity. In nine anesthetized cats, hypopharyngeal pressure and proximal esophageal pressure were recorded with a solid state transducer assembly. Enzymatic activities in the thyropharyngeus. cricopharyngeus, and proximal esophageal muscles were measured. Hypopharyngeal pressure was higher than the proximal esophagus (P<0.01), and choline acetyltransferase activity was higher in the cricopharyngeus compared to the proximal esophagus (P<0.05). The pressure gradient between the hypopharynx and proximal esophagus may be influenced by the activity of choline acetyltransferase.