To (1) categorize histologic esophageal myenteric plexus abnormalities in patients undergoing surgical treatment for epiphrenic diverticulum, and (2) correlate histologic changes with associated esophageal motility disorders and hiatal hernia.From January 1987 to May 2008, 40 patients had surgery for epiphrenic diverticulum. Esophageal manometry was abnormal in 29 (73%); 23 (58%) had hiatal hernia. Esophageal muscle specimens were evaluated for ganglion cell number, myenteric inflammations and myenteric fibrosis.Myenteric plexus abnormalities were present in 31 (78%). Ganglion cells were reduced in 8 (20%) and absent in 13 (33%). Myenteric inflammation was present in 21 (53%) and myenteric fibrosis in 9 (23%). Abnormalities were seen in 10 (83%) with motility disorders only, 5 (83%) with hiatal hernia only, 13 (76%) with both, and 3 (60%) with neither. Abnormalities in diffuse esophageal spasm (n=3) were similar to those of achalasia (n=14). Ineffective esophageal motility (n=6) was strongly associated with hiatal hernia, and abnormalities were similar to those of hiatal hernia without motility disorders (n=6). All patients with nutcracker esophagus (n=3) had hiatal hernia and histologic abnormalities, and two patients with hypertensive lower esophageal sphincter (n=3, hiatal hernia in 2) had myenteric inflammation.Myenteric plexus abnormalities predominate in epiphrenic diverticulum. Disease-specific patterns exist, but are incomplete. These associations and patterns point to causes of distal obstruction, with some commonality. In the absence of associated disorders, myenteric plexus abnormalities may be the sole finding. Isolated epiphrenic diverticulum is uncommon and may reflect an inability to detect abnormalities by current investigative techniques.