Bihar is one of the most economically deprived states in India. Home to nearly 10 per cent of India’s population, it consistently ranks poorly on a variety of development and health-related indicators. In order to improve child survival and decrease childhood mortality, it is important to understand the determinants of healthcare use so that appropriate policies may be developed to maximize health services utilization. This paper undertakes such as analysis. It uses the Andersen Behavioral Model to understand determinants of health services utilization for children suffering from diarrhea and respiratory illness in rural Bihar. Data were abstracted from the Second National Family Health Survey (NFHS-2). Out of 2703 children under 3 years of age in the dataset, 840 had an episode of diarrhea and/or respiratory illness in the preceding 2 weeks. A majority (69 per cent) had utilized healthcare services for their illness. The results indicate that controlling for other factors, sex of the child, household standard of living, service availability and need, are significant determinants of health service utilization. The analysis highlights the usefulness of the NFHS-2 data as a tool to conduct health services research and analyses at the state level, and in developing policies to safeguard and improve the health of vulnerable population groups in India.