Functional tests of the esophagus have become increasingly popular over the last 10 years. Here we present a cost/benefit analysis model to evaluate the real contribution to diagnosis with reference to the cost of these tests. All of the patients referred to the digestive physiopathology laboratory at the Institute of Surgical Semiotics, from 1988 to 1990, were evaluated for gastroesophageal reflux disease (152 cases), dysphagia (27 cases) and chest pain (12 cases). The cost of each modified diagnosis was L. 508,250 in the first case, L. 315,772 in the second case and L. 262,446 in the third case. Additionally, concerning gastroesophageal reflux disease, the cost of medical therapy based on endoscopic diagnosis alone was compared to that of medical therapy guided by these functional tests. Hence it was demonstrated that it is economically advantageous to study functionally all of the symptomatic patients, except the cases of esophagitis, and patients with atypical symptoms or with mild symptoms and endoscopic esophagitis of the first degree. It is not worthwhile investigating patients with second, third or fourth degree esophagitis, regardless of the symptoms, and patients with typical severe symptoms and first degree esophagitis. These functional tests are economically practical in all cases in which morphologic alterations are either absent or minimal.