In 2011, World Health Organization (WHO) scientists reported that a significant percentage of global deaths and disability-adjusted life years (DALYs) in 2004 could be attributed to chemicals. The 2011 review focused only on certain chemicals, however, and concluded that the global burden of disease was underestimated because of serious data gaps. While various chemical assessment documents have identified research needs for individual chemicals, a systematic review of such documents to identify research themes that could be applied to the multitude of chemicals for which there is little information has not been done. Even for chemicals for which there are considerable data, the information is not sufficient to make an estimate of the chemical's contribution to the burden of disease. The WHO Environmental Health Criteria (EHC) documents and Concise International Chemical Assessment Documents (CICADs) identify research needs or data gaps in our knowledge of chemicals. We identified several common themes in these documents and in documents prepared by WHO on 10 chemicals of major public health concern. These themes include biomarkers, longitudinal epidemiological studies, mechanisms of disease, reproductive and developmental effects and exposure assessment. Specific examples of data gaps culled from more than 300 WHO documents provide researchers with specific topics for further research.