Synthesis of research findings has a long-standing tradition in science. While synthesis is currently required in the US food and drug regulatory process, formal meta-analysis may substitute for a pivotal study or broaden the generalizability of drug efficacy through a preplanned meta-analysis. Preplanned meta-analysis of individual trials with deliberately introduced heterogeneity may maximize the generalizability of results from randomized trials. Combining observational data may help to support an alternative claim or to quantify adverse events. In this setting, methods to address potentially greater sources of bias are required. Overall, meta-analysis adds evidence through the synthesis study findings and permits examination of how treatment effects vary across of subgroups, such as age and sex, and across study settings.