INTRODUCTION: Obstructive sleep apnea syndrome (OSA) occurs in 2-4% of adults, increasing by 2.5 times the risk of sudden death. OBJECTIVE: Establish the concordance of the clinical diagnostic and electrical diagnosis in an adult series that underwent polysomnography. MATERIALS AND METHODS: Patients with sleep disorders that underwent consecutively polysomnography recording. RESULTS: In this study, 51 subjects from 24 to 77 years old (54.1±12.12) were included in the study; 23 males and 28 females; 78.43% were overweight or obese; 35.29% were smokers; 31.37% alcohol consumers; 47.05% hypertensive; 21% diabetics; 35.29% with airway alterations; 29.41% with depression; 13.72% dyslipidaemic and 7.84% with ischemic heart disease. Only 22 of the subjects qualified for OSA and the concordance between the clinical diagnostic and polysomnographic recording was 54% (Ko=0.60, Ke 0.50, Ka=0.20) with a 0.55 sensibility, 0.66 specificity, PPV 0.54, NPV 0.65, PLR 1.2, RVN 0.69 and PPP 0.47. The neck circumference in OSA was 40.68±5 vs. 37.7±3.5 cm. (p<0.02) and BMI was 36.48±13.16 vs 29.37±6.58 (p<0.008); male/female proportion was 1.8:1 (p<0.01), BMI was higher in OSA (p<0.002). The Epworth Sleepiness Scale did not discriminate between OSA and other sleep alteration (p<0.29). DISCUSSION AND CONCLUSIONS: We observed a poor agreement between clinical diagnosis and polysomnography. The Epworth Sleepiness Scale did not discern between OSA and other sleep disorders and finally there was no association with a systemic process.