Rosiglitazone (Avandia) is currently used in the treatment of Type 2 Diabetes. In recent years, there has been evidence to suggest that patients taking Rosiglitazone may have a higher rate of adverse cardiovascular events than patients taking a comparable treatment or placebo. However, ascertaining whether an increased risk exists has proven difficult, partly due to the fact that cardiovascular events are rare and no single clinical trial contains enough information to accurately estimate the risk. A meta-analysis combining the results from many clinical trials would seem to go some way to addressing this problem, but several issues remain including small sample sizes, the multiplicity of combinations of comparators or add-on treatments for diabetes, and heterogeneity of study designs.