Background: Hantavirus cardiopulmonary syndrome (HCPS) is caused by new world hantaviruses, among which Andes hantavirus (ANDV) is endemic to Chile and Southern Argentina. The disease caused by ANDV produces plasma leakage leading to enhanced vascular permeability and has a high case fatality rate (35%), mainly due to respiratory failure, pulmonary edema and myocardial dysfunction, hypoperfusion and shock. Host sociodemographic and genetic factors might influence the course and outcome of the disease. Yet, they have not been thoroughly characterized. Aim: To evaluate sociodemographic factors as risk factors in severity of HCPS. Patients and Methods: Study period: 2004-20013, attending in eight collaborative centers, etiological diagnosis was performed by serology or molecular biology, mild and severe HCPS were compared.139 Chilean patients were analyzed, 64 (46%) with severe disease among which 12 (19 %) died. Results: European ethnicity had 5,1 times higher risk than Amerindian ethnic group to develop a severe HCPS, greater seriousness that was also associated with an urban residence. Conclusion: It was observed that ethnicity and type of residence were significant risk factors for HCPS severity. Hypotheses explaining these findings are discussed.El síndrome cardiopulmonar por hantavirus (SCPH) es causado en Chile y en el sur de Argentina por el Andes hantavirus (ANDV), el cual es endémico en esta zona. La enfermedad causada por ANDV produce un aumento de permeabilidad vascular y filtración de plasma con una alta tasa de letalidad (35%), debido principalmente a insuficiencia respiratoria por edema pulmonar y al desarrollo en los casos severos de compromiso miocárdico, hipoperfusión y shock.  Aunque se sabe que los factores sociodemográficos del hospedero pueden influir en el curso y el resultado de la enfermedad, estos no se han caracterizado previamente en la población chilena. Este estudio tiene como objetivo evaluar la relación entre los factores sociodemográficos y la gravedad del SCPH. Se analizaron 139 pacientes chilenos, 64 (46%) con enfermedad grave, entre los cuales 12 murieron (19%).  Se observó una asociación estadísticamente significativa entre etnia, lugar de residencia y evolución de SCPH.