Acute respiratory infections (ARI) range, in spectrum, from mild colds and coughs to life-threatening pneumonias. ARI particularly pneumonia is the major cause of morbidity and mortality among young children. It is estimated that more than 150 million episodes of pneumonia occur every year among children under five in developing countries, accounting for more than 95 per cent of all new cases worldwide. Between 11 million and 20 million children with pneumonia will require hospitalization, and more than 2 million will die from the disease. It is also important to note that incidence of pneumonia among children decreases with age. Objective: To identify some of the risk factors for severe pneumonia in under five children. Materials and Methods: Cross-sectional, observational, hospital based casecontrol study conducted at Vijayanagara Institute of Medical Sciences hospital, Bellary. The study period was one year from 1-02-2011 to 31-01-2012. Results: The significant socio-demographic risk factors were low education level of parents, low socioeconomic status, and incomplete immunization for age. Significant environmental risk factors were use of biomass fuel (OR-2.49 95% CI 1.7-3.7) and overcrowding (OR-2 95% CI 1.4-2.8). Significant nutritional risk factors were low birth weight (OR-1.5 95% CI 1.1-2.7), pre-lacteal feeding (OR-2.94 95% CI 1.9-4.5), lack of exclusive breast feeding for 4-6 months and malnutrition. On multivariate analysis younger age (p=0.019), incomplete immunization for age (p=0.00), low literacy level of mother (p=0.00) overcrowding (p=0.004), use of biomass fuels (p=0.00), prelacteal feeding (p=0.00), lack of exclusive breast feeding (p=0.00) and malnutrition (p=0.00) have shown significant association with severe pneumonia. The present study has identified various sociodemographic, nutritional and environmental risk factors for severe pneumonia which can be reduced by effective education of the community and through appropriate public health measures.