BACKGROUND Little is known about the clinical significance of upper esophageal sphincter (UES) motility disorders and their association with the treatment response of type II achalasia. None of the three versions of the Chicago Classification of Esophageal Motility Disorders has defined UES abnormality metrics or their function. UES abnormalities exist in some patients and indicate a clinically significant problem in patients with achalasia. OBJECTIVE To demonstrate the manometric differentiation on high-resolution esophageal manometry between subjects with abnormal UES and normal UES, and the association between UES type and the treatment response of type II achalasia. METHODS In total, 498 consecutive patients referred for high-resolution esophageal manometry were analyzed retrospectively. The patients were divided into two groups, those with normal and abnormal UES function. UES parameters were analyzed after determining lower esophageal sphincter (LES) function. Patients with type II achalasia underwent pneumatic dilation for treatment. Using mixed model analyses, correlations between abnormal UES and treatment response were calculated among subjects with type II achalasia. RESULTS Of the 498 consecutive patients, 246 (49.40%) were found to have UES abnormalities. Impaired relaxation alone was the most common UES abnormality (52.85%, n = 130). The incidence rate of type II achalasia was significantly higher in subjects with abnormal UES than those with normal UES (9.77% vs 2.58%, P = 0.01). After pneumatic dilation, LES resting pressure, LES integrated relaxation pressure, and UES residual pressure were significantly decreased (41.91 ± 9.20 vs 26.18 ± 13.08, 38.94 ± 10.28 vs 16.71 ± 5.65, and 11.18 ± 7.93 vs 5.35 ± 4.77, respectively, P < 0.05). According to the Eckardt score, subjects with type II achalasia and abnormal UES presented a significantly poorer treatment response than those with normal UES (83.33% vs 0.00%, P < 0.05). CONCLUSIONS Impaired relaxation alone is the most common UES abnormality. The incidence of type II achalasia is associated with abnormal UES. Type II achalasia with abnormal UES has a poorer treatment response, which is a potentially prognostic indicator of treatment for this disease.