INTRODUCTION: The National Constitution assures every Brazilian citizen the right to health promotion and treatment. However, continuous positive airway pressure (CPAP) ventilation involves high costs for the healthcare system. Aim: To analyze CPAP prescription criteria, patients' waiting time, treatment compliance, and clinical improvement in a public hospital in Brazil. Methods FMB is the only Sleep Service in the public healthcare system for 2 million people. We analyzed the charts of patients on ambulatory CPAP for OSA severity, co-morbidities, details of the CPAP prescription, patient's waiting time, compliance, and clinical improvement over a 3-year period from 2010 to 2012. RESULTS: Two hundred and seventy-eight patients had been evaluated for CPAP treatment. Their mean age was 52 years; 34% had been diagnosed with severe OSA; and the most frequent co-morbidities were obesity and hypertension. Only 115 (54.9%) had already received CPAP at the time of survey, and the waiting time was 9.15 ± 5 (mean ± SD) months; the longest waiting period was 21 months. 92% of patients received the prescribed CPAP correctly and 78% got the prescribed mask. Follow-up at 3-month intervals showed that only 13.1% of patients had adverse effects, the most common of which was difficulty in adapting to the prescribed mask, and most patients adhered to treatment by using CPAP for more than 4 h every night. CONCLUSION: Access to Sleep Centers is insufficient in the Brazilian Public Health System and the waiting time for receiving CPAP is very long; this is a matter of concern considering the high percentage of severe disease among OSA patients. Most prescribed masks did not fit properly leading to difficulty in adaptation. Close follow-up is necessary for good compliance, but only few hospitals offer attendance.