Introduction: According to the World Health Organization, there are 15 million people with hearing loss in Brazil and, among them, about 350,000 are deaf. The Deafness Prevention League of the São Paulo University School of Medicine was created with the purpose of prevention. Objective: To evaluate the first three years of the Deafness Prevention League. Material and Methods: We analyzed 277 patients attended at the League from 1997 to 2000. Patients were divided into 4 groups according to their age, and analyzed by etiology in each group and total. Results: There were 273 with hearing loss. Fifty six percent were due to infections, 26% sensorineural hearing loss (excluding infections), 7,6% otosclerosis, 4,7% malformations, 2,9% of tumoral cause and 2,1% traumatic. Considering age, there were a predominance of infectious etiology and malformations in the younger than 40, otosclerosis and trauma in the group between 40 e 60, and sensorineural causes in patients older than 60. Conclusion: Most of the cases of hearing loss have infectious etiology, usually with exuberant clinical manifestations. Patients who complained of isolated hypoacusis were very few. As we work in a tertiary hospital, more patients with ototoxicity, presbiacusis and at risk for hearing loss should be referred. We conclude that there should be a better divulgation of the problem to other medical specialties.