Hypersomnia is one of the most consulted symptoms among patients evaluated at sleep disorder centers and it is frequently related to obstructive sleep apnea syndrome (OSAS). Our hypothesis is that Epworth sleepiness scale (ESS) is the parameter with the greatest predictive value in the OSAS diagnosis. We compared patients with OSAS diagnosis to a control group. In both groups we compared ESS with body mass index (BMI), neck circumference (NC), waist perimeter (WP). Anthropometric index (BMI, NC and WC), were similar in both groups (p < 0.10). When we analyzed ESS, a score greater than 10 was observed in the OSAS group, with a significant difference between groups (p < 0.001). Epworth sleepiness scale yielded 60% of sensibility, 82% of specificity and a positive predictive value of 85%. The negative predictive value was 52%. Confidence index was 70%. The relationship between OSAS and ESS scale was significant (Pearson Chi-Square value 7.5). Odds Ratio for apneas was 15 and its confidence interval was lower than 1.5 and upper than 141. We conclude that with ESS score exceeding 10 points OSAS should be suspected.