"Abstract: General belief that acute pneumonia and acute dehydrating diarrhea being responsible for majority of post neonatal under 5 (PNU5) deaths can be easily preventable through simple intervention like oral anti-microbials and rehydrating fluids has been well accepted in all low resource setting like state of Bihar with population of 115 million, India. To understand magnitude of under-five mortality and its preventable fraction, a study was launched in two districts of Bihar. Due to lack of completeness of available sampling frames, entire area of nine Health Subcentre (>one lac population) was taken by stratified random sampling. After verifying for reference age and period, verbal autopsy was conducted for 116 neonatal and 60 PNU5 deaths out of 134 and 63 respectively. Among PNU5, only 4 and 3 deaths were attributed to acute respiratory illness and acute dehydrating diarrhea (preventable through conventional programmatic measures) respectively. There were 17 deaths with variety of diagnosis of short duration (<7 days). There were 9 and 17 deaths with complex illnesses of moderate (1-2 weeks) and prolonged (>2 weeks) duration respectively. Barring 2 trauma and 8 sudden deaths, care wasn't sought for few cases (n=6) and promptly sought for majority of cases (n=37). Narrations confirmed a sense of urgency, understanding for severity and dedication for care seeking from parents. Among neonates, around 80% of deaths occurred within a week of birth primarily due to asphyxia, preterm and low birth weight. Around 25% of deaths occurred due to infections and almost one third due to prematurity. Key words: Communicable diseases, Primary Health Care, Evaluation, Research/knowledge translation, Key messages: 1. Neonatal mortality and Post Neonatal Under 5 mortality were higher and lower respectively than expected. 2. Conventional public health approaches to tackle under 5 mortality may require further strengthening to reach goals. 3. To reach that target, new contextualized interventions and strategies may be designed, tested and implemented. "