Patients with achalasia develop a well-defined obstructive pattern of pressure in response to a rapid drink challenge test (RDC). Our aim was to determine if successful treatment of achalasia can revert the obstructive pattern of pressure in response to the RDC, and if this simple test could be useful in the follow-up of patients with achalasia. In 26 healthy controls and 103 patients with achalasia, pressure responses to a RDC were prospectively analysed using high resolution esophageal manometry in two consecutive protocols: (a) Development study: one RDC was performed in 20 healthy controls, 63 patients with nontreated achalasia, and 21 patients with previously treated achalasia; (b) Validation study: two RDC were performed before, and 8-12 weeks after treatment, in 19 patients with nontreated, newly diagnosed achalasia. In the development study no healthy control, 19% of patients with previously treated achalasia and 96% of patients with nontreated achalasia developed an obstructive pressure pattern during the RDC (P < 0.001). In the validation study, 100% of patients had an obstructive pressure pattern before treatment, that reverted to a nonobstructive pattern in 89% of patients after treatment (P < 0.001). The obstructive pressure pattern during the RDC correlated with clinical symptoms (Eckardt score > 3; P < 0.001), and with the height of the water column retained after the RDC, as assessed by impedance (P = 0.015). The RDC may objectively assess treatment outcome in patients with achalasia, and can be recommended in the evaluation of achalasia.