conclusion Our results suggest an association between pioglitazone use and bladder cancer in adults with diabetes Given the limited evidence among rosiglitazone users, it remains unclear if the association with bladder cancer is a class effect of all thaizolidinediones. Evidence surrouding the assosiation between pioglitazone and bladder cancer requires caution interpretation, because our evidence is based on only three,albeit large and well-conducted,odservational studies.