Sleep-disordered breathing are frequent processes in Spain. Among them, the obstructive sleep apneas are the best known although not all studies are performed with the same diagnostic criteria with regard to the percentage of apneas and hypopneas per hour of sleep and the need to consider the presence or absence of clinic symptoms. After a reference to the biggest epidemiologic studies performed in different populations, the data of the major populational studies in our environs are analyzed.