To assess the burden of neonatal mortality in two developing regions. Review of secondary data collated through literature review. Community and facility based studies and national health surveys. Neonatal (<28 days) population of South Asia and Sub-Saharan Africa. Data on neonatal mortality were gathered from peer-reviewed literature, reports of the Demographic and Health Surveys and websites of country-based organisations. The base year for this study is 1995. For each country, a weighted mean neonatal mortality rate was calculated and the total number of neonatal deaths estimated. Country data were summarised over each region to estimate annual regional neonatal deaths and rates. The burden of disease from neonatal mortality was determined using a summary measure of health--healthy life years. Numbers of deaths and healthy life years (HeaLYs). Neonatal mortality rate for South Asia ranged from 41.9 to 56.9 per 1000 live births for 1995. Sri Lanka was an exception with a neonatal mortality rate between 16.3 and 18.6 per 1000 live births. The estimated regional neonatal mortality rate for South Asia was 46.27 per 1000 live births for 1995. There was a significant lack of data from Sub-Saharan Africa, resulting in highly variable neonatal mortality rates, ranging from 13 per 1000 live births in Kenya to 108 per 1000 live births in Senegal. The mean regional neonatal mortality for Sub-Saharan Africa for 1995 was estimated at 38.8 per 1000 live births. The burden of neonatal mortality in only these two regions of the developing world represents more than 2 million annual deaths. A call for greater investments in neonatal research and health programs is a logical extension to this review of evidence.