Obstructive sleep apnea (OSA) is a prevalent condition. OSA is defined as very severe when the apneas/ hypopneas index (AHI) is greater than 60 events/hour. However, its prevalence remains uncertain. The aim of this study was to describe the prevalence and characteristics from patients with OSA according to severity. We performed a retrospective analysis of patients > 18 years, assessed by respiratory polygraph. We evaluated a total of 5670 patients with a mean of age of 54.4 ± 14.3 years old, of which 3606 were included in the OSA group. The overall prevalence of very severe OSA was 4.8%, being higher in men than in women (6.8 vs 1.9%). This group of patients was younger than the less severe groups (54.7 ± 13.9: mild OSA; 56.5 ± 12.9: moderate OSA; 57.9 ± 13.0: severe OSA vs 51.5 ± 12.9 years in the very severe patients; p < 0.0001). The results showed a significant increase in the body mass index (BMI) of patients with very severe OSA (31.6 ± 6.9: mild OSA, 32.8 ± 6.6: moderate OSA, 34.0 ± 6.8 severe OSA vs 37.1 ± 8.5 extreme severity; p 10, showed a significant increase in the very severe group of both sexes; 43.2% vs 31.5% (severe OSA); 26.4% (moderate OSA) and 23.8% (mild OSA). Very severe OSA presented a prevalence of 4.8% of patients with OSA. According to previous publications in other studied populations, we found that patients with very severe OSA are younger and more obese than the less severe groups.