This paper focuses on the importance data issues to the analysis of growth, poverty and economic inequality. We introduce a number of major databases frequently used in applied research on growth, poverty and global and international inequality. A discussion of data quality, data consistency, variable definitions and measurement, changing population and household size leading to various necessary scale and price adjustment procedures will follow. The sampling design and various dimensions of sample dependency are also discussed. Based on the existing experience we identify a number of factors that are important in applied research. The focus is on these factors which impacts on reliability, precision, sensitivity and consistency of the results and conclusions drawn.