espanolIntroduccion: Para el 2007 en Colombia se estimo que el 56% de la poblacion adulta era obesa, condicion que se considera un problema de salud publica con implicaciones en el desarrollo de enfermedad coronaria. Objetivo: Determinar la distribucion de las frecuencias alelicas y genotipicas y la relacion del polimorfismo rs4998 del gen ADRB3 con el indice de masa corporal en una poblacion de docentes y administrativos. Materiales y Metodos: La extraccion de ADN se llevo a cabo mediante un metodo comercial, para la amplificacion de ADN se emplearon cebadores especificos no marcado con fluorocromos, los fragmentos obtenidos fueron purificados mediante las enzimas SAP y EXOSAP, finalmente se realizo minisecuenciacion en el ABI PRISM 310 y posterior lectura de electroferogramas. El analisis de las variables sociode mograficas se realizo mediante metodos univariados y metodos bivariados empleando pruebas de significancia como: test Chi2 de Pearson y test exacto de Fisher. Modelos logisticos fueron empleados para evaluar asociacion. Resultados: Las frecuencias genotipicas encontradas fueron 0.96 GG, 0.014 CG y 0,020 CC. Las frecuencias alelicas fueron 0,027 C y 0,973 G. La muestra se encontro en equilibrio de Hardy-Weinberg con Chi2 = 81.153(1) (p = 0.000) y se calculo la estructura poblacional mediante la prueba Fst = 0,743. Discusion: Encontrar la poblacion en equilibrio de Hardy-Weinberg indica que los individuos se estan mezclando al azar. El coeficiente de endogamia o estadistico Fst, indica que la poblacion presenta una alta estructura o diferenciacion genetica y existe fijacion del alelo mutado G; esto podria obtener falsas asociaciones con la patologia de interes. Conclusion: Las frecuencias obtenidas en este estudio no se ajustan a los modelos genicos propuestos para estudios de asociacion; por lo tanto, se recomienda aumentar el tamano de la muestra para futuras investigaciones o plantear estudios de casos y controles. EnglishIntroduction: At 2007 in Colombia it was estimated that a portion 56 % from the adult population was obese, a condition that is considered a public health problem with implications in the development of coronary heart disease.Objective: Determine the distribution of allelic and genotypic frequencies and the relation of the polymorphism rs4998 of the ADRB3 gene with the Body Mass Index in a population of teachers and administrators of an university institution in Colombia. Methods: DNA extraction was carried out by a commercial method, for specific DNA amplification, specific primers not labeled with fluorochromes were used, fragments obtained were purified by SAP and EXOSAP enzymes, and finally minisequencing was performed in the ABI PRISM 310 and later electropherogram reading. The analysis of the sociodemographic variables was performed using univariate methods and bivariate methods using significance tests such as: Pearson’s Chi2 test and Fisher’s exact test. Logistic models were used to evaluate association. Results: The genotype frequencies found were 0.96 GG, 0.014 CG and 0.020 CC. The allele frequencies were 0.027 C and 0.973 G. The sample was found in Hardy-Weinberg equilibrium with Chi2 = 81.153 (1) (p = 0.000) and the population structure was calculated by means of the Fst test = 0.743. Discussion: Finding the population in Hardy-Weinberg equilibrium, indicates that individuals were mixed randomly. The coefficient of inbreeding or statistical Fst, is very close to one, which indicates that the population has a high structure or genetic differentiation and there is fixation of the mutated allele G. This could obtain false associations with the pathology of interest. Conclusion: The frequencies obtained in this study do not fit the proposed gene models for association studies, therefore, it is recommended to increase the sample size for future researches or to propose case-control studies.