Introduction: The full night polysomnography (PSG) in sleep lab is the gold standard to Obstructive Sleep Apnea (OSA) diagnosis. However, there is a need to evaluate simple and accurate home diagnostic equipment that can reliably detect or exclude OSA. The aim of our study was to evaluate if an ambulatory portable monitor (SD) is accurate to measure apnea-hypopnea index (AHI) in OSA patients referred to a Sleep Lab. Methods: Patients with clinical suspicion of OSA were selected. Three-order randomized evaluations had been performed within a period of two weeks: the 1) SD (Stardust®, Respironics, Inc, USA) was used at patients home (SD home), 2) SD was used simultaneously with PSG in the sleep lab (SD+PSG lab) and 3) PSG was performed without the use of SD (PSG lab). Four AHI were generated and analyzed: AHI from SD home, AHI from SD of SD+PSG lab, AHI from PSG of PSG+SD lab and AHI from PSG lab. The analyses of SDs and PSGs recordings were performed by two blinded technicians.