Background:Pneumonia in children under five years old is a health problem in Indonesia. It is associated with high morbidity and mortality due to pneumonia. One of the control efforts are in recognition of the determinant factors of pneumonia in children under five, so the reduction and prevention of this disease can be done properly. This paper aims to outline some of the determinant factors of pneumonia in children under five years old in the province of East Nusa Tenggara include immunization status, nutritional status and healthy home. Methods:The data used are secondary data Provincial Health Office of East Nusa Tenggara in 2012 include data cases, nutritional status, immunization, exclusive breastfeeding and healthy home were analyzed. Results: The results indicate the scope of discovery and handling pneumonia in children under five in 2012 amounted to 19.2%, a factor of determination relating to pneumonia incidence was 59% complete immunization status, Nutritional status is less their 12.6%, 1.4% severe malnutrition, coverage exclusive breastfeeding is 49.7%, and 61.1% coverage of a healthy home. Conclusion: Cases of pneumonia in children under five in NTT has increased in 2012. The condition factor of immunization status, coverage Exclusive breastfeeding, nutritional status be a factor supporting the occurrence of pneumonia in under five. Recommendation: Suggested an improve in education about pneumonia, exclusive breastfeeding, toddler nutrition and the importance of immunization and growth monitoring sessions mobilize the community in a way increased participation posyandu cadres so as to improve immunization status and improvement of nutritional status of children under five years old.