The objective of this study was to evaluate compliance with the use of the CPAP machine in a sample of Greek patients with SAHS, as well as to investigate which factors influence compliance in these patients. We studied 138 consecutive patients (114 men, 24 women, mean age±SD: 52±10 years) who were scheduled for a follow up visit in the last 3 months of the year 1999. The single one eligibility criterion was the presence of an integral time clock in the CPAP machine. The patients had the machine in their possession for 20 to 2,315 days (mean value: 379 days). The total time of CPAP use was 57 to 14,388 hours (mean value: 1733 hours), while daily CPAP use varied from 0.429 to 10.08 hours (mean: 5.54 h/day). Analysis of study data showed that 77.5% of the patients used the CPAP machine for more than 4 hours daily; adjusted compliance was 77%. Apnea/hypopnea index (AHI) was the only parameter that correlated with daily use (p<0.01) and adjusted compliance (p<0.03). An inverse significant correlation between adjusted compliance and duration of CPAP treatment was found. Women used the CPAP machine for a shorter daily time, showed lower adjusted compliance [64±27 vs. 80±28 (p<0.02)] and reported more problems with their partners (p=0.0014) compared to men. Conclusively, the studied sample of Greek SAHS patients shows a generally satisfactory compliance with CPAP therapy, which is similar to that reported in the literature. However, women adduce a variety of reasons to justify their low CPAP use, even though they have accepted this treatment. Pneumon 2004, 17(2):167-176.