BACKGROUND: Achalasia is characterized by a functional esophagogastric junction (EGJ) obstruction. The functional luminal imaging probe (EndoFLIP) is a method to assess EGJ distensibility. In a homogeneous group of newly diagnosed achalasia patients treated with pneumatic dilation (PD), we aimed (i) to determine whether the assessment of EGJ distensibility has added value in the management of achalasia patients and (ii) to evaluate whether EGJ distensibility differs between achalasia subtypes. METHODS: Twenty-six newly diagnosed achalasia patients were treated by graded PD (30 and 35 mm) separated by 1 week. EGJ distensibility was measured with the EndoFLIP technique before and after 30 mm PD. Good clinical outcome was defined as an Eckardt score <4 at 1-year follow-up. Fifteen healthy controls underwent an EndoFLIP measurement as control group. KEY RESULTS: Newly diagnosed achalasia patients had reduced EGJ distensibility compared to healthy controls (0.9 [0.7-1.5] vs 3.4 [2.7-4.2] mm(2) /mmHg, p < 0.01), and EGJ distensibility was lower in type II compared to type I patients (0.8 [0.7-1.1] vs 1.5 [0.9-1.9] mm(2) /mmHg, p = 0.02). EGJ distensibility was increased after PD from 0.9 (0.7-1.5) to 4.2 (3.0-5.7) mm(2) /mmHg (p < 0.001). No difference was found in EGJ distensibility directly after PD between patients with good and poor clinical outcome at 1-year follow-up. CONCLUSIONS & INFERENCES: Assessment of EGJ distensibility with the EndoFLIP technique is able to demonstrate the functional EGJ obstruction in newly diagnosed achalasia patients and EGJ distensibility differs between achalasia subtypes. Although PD improves EGJ distensibility, assessment of EGJ distensibility with a limited number of distension steps provides no additional information that is useful for clinical evaluation and management of achalasia patients.