Introduccion: el sueno es una funcion fisiologica importante para el adecuado funcionamiento fisico, sicologico, cognoscitivo e intelectual. La somnolencia diurna excesiva de tipo moderada o grave es un disturbio del sueno y su presencia en estudiantes de medicina, pudiese repercutir en el rendimiento academico. Objetivo: establecer la prevalencia de somnolencia diurna normal y patologica en estudiantes de pregrado de medicina. Metodologia: estudio de corte transversal prospectivo. Se incluyeron estudiantes de pregrado de medicina de la Universidad de Cartagena, Colombia, en el segundo periodo academico del ano 2011. Se les aplico un formulario para recoleccion de informacion socio demografico, academica y la escala de Epworth para evaluar somnolencia diurna. A mayor puntuacion mayor somnolencia diurna. La participacion fue voluntaria y anonima, escogiendose una muestra estratificada por sexo y semestre. Los datos fueron analizados con Epi-Info 3.5.1. Valor de p<0.05 fue considerado estadisticamente significativo. Resultados: 210 estudiantes de medicina llenaron completamente los formularios. Edad media 19.7±2.0. El 51.0% [IC95%: 44.0-57.9%] femenino y 49.0% [IC95%: 42.1- 56.0%] masculino. El 69% [IC95%: 62.3-75.2%] procedente de Cartagena y el restante 31% [IC95%: 24.8-37.7%] de distintas provincias. El 53.8% [IC95%: 49.8%-60.7%] con vida sexual activa. El promedio academico de toda la poblacion de estudiantes fue 3.8±0.28. El 31.4% [IC95%: 25.2%-38.2%] con notas altas, 50.5% [IC95%: 43.5%- 57.4%] notas medias y el 18.1% [IC95%: 13.1%-24.0%] notas regulares. No tuvieron somnolencia diurna anormal el 19.0% [IC95%: 14.0%-25.0%], el 21.4% [IC95%: 16.1%-27.0%] presentaron excesiva somnolencia diurna leve, el 49.0% [IC95%: 42.1%- 56.0%] moderada y el 10.5% [IC95%: 6.7%-15.4%] grave. El 60% de los estudiantes tenia somnolencia diurna patologica. La puntuacion promedio de la escala de Epworth en la poblacion fue 10.6±3.7. Se observo diferencia significativa de somnolencia diurna segun estado nutricional. La puntuacion promedio de la escala en estudiantes de bajo peso fue 9.1±3.1, peso normal 10.6±3.7, sobrepeso 11.5±3.9 y obesidad 5.5±2.1 (p=0.03). Tambien se observo diferencia significativa segun actividad sexual, 11.3±3.9 en estudiantes con actividad y 9.7±3.3 en los que no tenian (p=0.002). No se encontro diferencia significativa en la severidad de la somnolencia diurna segun el rango de notas ni por nivel de formacion. Conclusiones: se observo que seis de cada diez estudiantes presentaban somnolencia diurna moderada o grave. No se encontraron diferencias en la severidad de la somnolencia diurna segun el rendimiento academico. Rev.Cienc.Biomed. 2013;4(1): 31-41. PALABRAS CLAVE Trastornos de somnolencia excesiva; Estudiantes; Medicina; Rendimiento escolar bajo; Sueno. SUMMARY Introduction: Sleep is an important physiological function for the adequate physical, psychological, cognitive and intellectual performance. Excessive daytime sleepiness classified as moderate or severe is a sleep disorder and its presence in medical students could affect in the academic performance. Objective: Establish the prevalence of normal and pathological daytime sleepiness in medical students. Methods: Prospective and cross-sectional study. Medical students of Medicine of the Universidad de Cartagena, Colombia in the second academic period of 2011 were included. A survey for the compilation of socio-demographic and academic data and the Epworth Scale for the assessment of daytime sleepiness were applied. The higher the score indicates higher daytime sleepiness of the respondent. The participation was voluntary and anonymous. A stratified sample by gender and semester was chosen. Data analysis was performed using the EPI-INFO statistical program (Version 3.5.1). A p value < 0.05 was considered as statistically significant. Results: 210 medical students filled completely the surveys. The mean age was 19.7±2.0 years. 51.0% [CI 95%: 44.0-57.9%] were women and 49.0% [CI95%: 42.1-56.0%] were men. 69% [CI95%: 62.3-75.2%] came from Cartagena and the remaining 31% [CI95%: 24.8-37.7%] came from different provinces. 53.8% [CI95%: 49.8%-60.7%] had sexually active life. The academic mean of all population of students was 3.8±0.28. 31.4% [CI95%: 25.2%-38.2%] had high grades, 50.5% [CI95%: 43.5%-57.4%] had average grades and 18.1% [CI95%: 13.1%-24.0%] had regular grades. 19.0% [IC95%: 14.0%-25.0%] did not have abnormal daytime sleepiness, 21.4% [CI95%: 16.1%- 27.0%] had mild daytime sleepiness, 49.0% [CI95%: 42.1%-56.0%] moderate daytime sleepiness and 10.5% [CI95%: 6.7%-15.4%] had severe daytime sleepiness. 60% of the students had pathological daytime sleepiness. The average score of Epworth scale in the population was 10.6±3.7. Significant difference of diurnal somnolence according to the nutritional status was observed. The average score of the scale in students with low weight was 9.1±3.1, normal weight 10.6±3.7, overweight 11.5±3.9 and obesity 5.5±2.1 (p=0.03). Also a significant difference according to the sexual activity was observed, 11.3±3.9 in students with sexual activity and 9.7±3.3 in those without it (p=0.002). There was not found significant difference in the severity of daytime sleepiness according to the range of grades and the academic level. Conclusions: It was observed that six of each ten students presented excessive daytime sleepiness classified as moderate or severe. There were not found differences in the severity of the diurnal somnolence according to the academic performance. Rev.Cienc.Biomed. 2013;4(1): 31-41. KEYWORDS Disorder of excessive somnolence; Students; Medicine; Underachievement; Sleep.