Objective: To analyse the efficacy of low-dose rosuvastatin for treating hypo high-density lipoprotein (HDL) cholesterolaemia in patients with type 2 diabetes and dyslipidaemia. Methods: Patients with HDL-cholesterol (C) <40 mg/dl and triglycerides (TG) <400 mg/dl who were receiving treatment with lipid-lowering drugs other than rosuvastatin (or previously untreated with lipid-lowering drugs) and with low-density lipoprotein [LDL]-C !120 mg/dl were included. Patients were treated with 2.5 or 5 mg rosuvastatin orally, once daily, to achieve the target LDL-C level specified in Japanese guidelines. Changes in total cholesterol, HDL-C, TG, LDL-C, LDL-C/HDL-C and non-HDL-C at 3 and 6 months were prospectively analysed. Safety was evaluated by examining changes in hepatorenal function, glucose metabolism and creatine kinase. Results: Out of 49 patients, all lipid parameters other than TG were significantly improved at 3 and 6 months. At 3 months, 83.3% of patients had achieved the target LDL-C level. Among nonlipid parameters, no changes were observed except for estimated glomerular filtration rate, which was improved by þ 5.2% and þ 9.6% at 3 and 6 months, respectively. Conclusions: Low-dose rosuvastatin was effective in improving hypo-HDL cholesterolaemia and may have renoprotective effects.