Chapter 61 Using Randomization in Development Economics Research: A Toolkit This paper is a practical guide (a toolkit) for researchers students and practitioners wishing to introduce randomization as part of a research design in the field. It first covers the rationale for the use of randomization as a solution to selection bias and a partial solution to publication biases. Second it discusses various ways in which randomization can be practically introduced in a field settings. Third it discusses designs issues such as sample size requirements stratification level of randomization and data collection methods. Fourth it discusses how to analyze data from randomized evaluations when there are departures from the basic framework. It reviews in particular how to handle imperfect compliance and externalities. Finally it discusses some of the issues involved in drawing general conclusions from randomized evaluations including the necessary use of theory as a guide when designing evaluations and interpreting results.