Lower esophageal rings are classified into two primary types. The A-ring is a thick, muscular ring found approximately 2 cm above the squamocolumnar junction. It marks the upper border of the lower esophageal sphincter (Fig. 5.1). Muscular A-rings are exceedingly rare. Although many clinicians consider them a variant of normal esophageal anatomy, they have been reported to cause dysphagia (1,2 and 3). Because the constriction caused by A-rings is secondary to muscular hypertrophy and not stricture formation, dilation is seldom successful at relieving the dysphagia. Botulinum toxin type A injections into the muscular ring have been shown to be beneficial but may result in a significant increase in reflux (3). Whereas the A-ring is muscular, the B-ring is a thin, annular membranous ring of mucosa associated with submucosal fibrosis at the gastroesophageal junction.