Objective: To determine physicians’ knowledge level on obstructive sleep apnea and to compare it with a report published in 2001. Design: Cross-sectional study. Setting: Five congresses developed during 2006. Participants: Congress assitants. Interventions: Questionnaire with 18 questions about knowledge of the syndrome. This questionnaire was self administered, unique and anonymous. Main outcome measures: Knowledge of the syndrome, its diagnosis and treatment. Results: Two hundred and forty-one questionnaires were successfully obtained. The age of the participants was 36,1±11,7 [20 to 76] years. Two hundred and thirty seven (98%) knew the meaning of ‘sleep apnea’, acquired in pre-degree studies in 39%; 16% identified disorders associated to the syndrome; 149 (62%) affirmed it appeared exclusively in obese men and 45 (19%) that it was most frequent in premenopausal women; 107 (45%...