Esophageal achalasia is characterized by the absence of esophageal peristalsis and by a dysfunctional lower esophageal sphincter (LES). Descriptions of clinical, radiological, and manometric findings in patients with achalasia usually have been based on small numbers of patients. This study was designed to determine in patients with untreated achalasia: (1) clinical presentation; (2) how often a diagnosis of gastroesophageal reflux disease (GERD) was erroneously made based on the presence of heartburn; (3) manometric profile; (4) relationship between chest pain and the manometric finding of vigorous achalasia. Between 1990 and 2004, a diagnosis of esophageal achalasia was established in 145 patients. None of them had been previously treated (no previous endoscopic or surgical treatment). We evaluated the demographic and clinical characteristics, as well as the results of the endoscopy, barium swallow, esophageal manometry, and ambulatory pH monitoring. We also compared the clinical and the manometric profile of patients with classic and patients with vigorous achalasia. Most patients with untreated achalasia had dysphagia (94%). Regurgitation was present in 76% and heartburn in 52%. Chest pain (41%) and weight loss (35%) were less common. Acid-suppressing medications had been prescribed to 65 patients (45%) who complained of heartburn on the assumption that GERD was present. The LES was hypertensive in 43% of patients only. There was no significant difference in the prevalence, severity, and duration of chest pain in patients with classic and with vigorous achalasia. These results show that in patients with untreated achalasia: (1) dysphagia was the most frequent complaint, but regurgitation and heartburn were frequently present; (2) a diagnosis of GERD based on the presence of heartburn was highly unreliable; (3) the LES was hypertensive in less than half of patients; and (4) the prevalence, severity, and duration of chest pain did not correlate with the manometric finding of vigorous achalasia.