The evidence suggests that, compared with placebo, pioglitazone is effective in reducing blood glucose in patients with inadequate glycaemic control, both when used as monotherapy and in combination with existing licensed therapies. However, there is no firm evidence to indicate that pioglitazone is more effective than any other antidiabetic agent, particularly when used in combination. Additionally, it is unclear how pioglitazone therapy affects the incidence of microvascular and cardiovascular complications.