To compare the effects of rosiglitazone and pioglitazone on patient lipid levels in a clinical practice setting, we retrospectively examined charts of 20 patients in our practice. The patients had been treated for type 2 diabetes for 3 or more months with rosiglitazone (4 mg b.i.d.) followed immediately by 3 or more month^s' treatment with pioglitazone (45 mg once daily). Glycaemic control was excellent and essentially equivalent during the two treatments. At baseline, the mean HbA1c level was 7.6%; it dropped to 6.6% and 6.3% with rosiglitazone and pioglitazone treatment, respectively. Lipid levels, however, differed with the two treatments. Triglyceride levels rose 13% with rosiglitazone treatment, but fell 14% below baseline levels with pioglitazone therapy - a 24% reduction overall (p = 0.02). Rosiglitazone was associated with a significant increase in low-density

lipoprotein cholesterol (LDL-C) levels (35%, p < 0.001 vs. baseline) and a significant increase in total cholesterol levels (22%, p < 0.001 vs. baseline). When pioglitazone replaced rosiglitazone therapy, LDL-C fell 25% (p < 0.001), and total cholesterol fell 19% (p < 0.001 between treatments). HDL-C levels did not change significantly during either treatment. Both drugs were otherwise safe and well tolerated. One patient receiving rosiglitazone and one receiving pioglitazone developed oedema that resolved without therapy discontinuation. Liver enzyme levels and blood pressure were unaffected in this group of patients. Because patients with diabetes are at risk for coronary artery disease, physicians should consider each agent's effects on lipid levels when choosing a specific thiazolidinedione.