The aim of this study was to compare home polysomnography (HoPSG) with laboratory polysomnography (LabPSG) in the diagnosis of sleep apnea syndrome (SAS). A total of 103 patients referred for investigation of SAS underwent two full polysomnographies, using the portable Minisomno device at home and the Respisomnographe in the laboratory (both devices manufactured by the same company). Twenty percent of home-studied device polysomnography (HoSD-PSG) recordings and 5% of LabPSG recordings were excluded from analysis either because of lost data or poor quality data. Sleep stage distribution and subjective quality of sleep were similar by both methods. Using LabPSG, the mean (+/- SD) RDI was 25.7 (+/- 30.6) versus 22.8 (+/- 31.5) using HoSD-PSG (p > 0.05). Absolute differences between the home and laboratory respiratory disturbance index (RDI) were less than 10 for 65% of patients. Discordant RDIs (i.e., differences greater than 10) were observed for 63% of individuals with severe SAS (RDI > 30) versus 22% of those with normal or moderate SAS (RDI </= 30) (p < 0.05). Higher RDI differences were associated with poor airflow signal at home. Forty-seven percent of patients preferred LabPSG. Our results suggest that HoSD-PSG was not feasible for 33% of patients; there was no evidence of a better quality of sleep and recording tolerance at home; the reliability of HoSD-PSG for SAS diagnosis depends on the quality of data obtained under unattended conditions.