Pneumatic dilation (PD) has been widely used in the treatment of idiopathic achalasia with a 70-90% response. The aim of this study was to evaluate the effectiveness of PD and its predictive factors by means of clinical assessment. In addition, we evaluated its safety and the need for subsequent surgical intervention. Fifty-six patients were treated with a Witzel dilator. The response was evaluated at medium (1-5 years) and long term (>5 years). Diverse possible predictive factors to response were analyzed. After the first PD, 85.7% of the 56 patients improved and passed from clinical stage II-III to clinical stage 0-I (P < 0.005). After the second dilation, 84.6% of the patients (13) passed to clinical stage 0-I (P < 0.05). Only patients who were not young (>40 years) avoided a second dilation and/or surgery (P < 0.001). During the first 5 years of follow-up, 80% of patients maintained their response; this percentage decreased to 58% after 10 years. PD therapy of achalasia is a safe technique, with few adverse effects (4% perforations and 10% gastroesophageal reflux). It offers a medium-term response of 80% and long-term response of around 60%. Age was the only predictive response factor.