This is a phase IV, randomized, open-label, parallel-arm, comparative and forced- titration study to compare the efficacy and safety of rosuvastatin versus simvastatin in patients with type 2 DM and dyslipidemia. When comparing the efficacy of rosuvastatin 20 mg with simvastatin 40 mg for the treatment of type 2 DM with dyslipidemia, rosuvastatin 20 mg is superior to simvastatin 40 mg in achieving the combined goal of LDL-C (<100 mg/dL) and non-HDL-C (<130 mg/dL).

The duration of patient participation will be 18 weeks consisting of a 1-week screening period, a 5-week lead-in period, followed by a 12-week treatment period.

Inclusion Criteria:

1. Male and female between the ages of 20-75 years.
2. Female patients post menopausal, hysterectomized or if of childbearing potential using a reliable method of birth control.
3. Diagnosed with type 2 diabetes mellitus.
4. Fasting triglyceride ≧150 mg/dL ≦500 mg/dL or Non-HDL-C≧130,but≦200 mg/dL
5. Patients receiving stable antidiabetic treatment for 8 weeks before randomization (no change in the category of anti-diabetic agents, but the dose is adjustable).
6. All patients give written informed consent.

Exclusion Criteria:

1. A history of hypersensitivity to statins.
2. A history of rhabdomyolysis or hereditary muscle disorders.
3. Insulin-treated patients.
4. Patient with any conditions of acute or chronic pancreatitis.
5. Creatine kinase ≧3-fold upper limit of normal (ULN).
6. Patients with an estimated creatinine clearance (see note)≦30 ml/min or bilirubin ≧1.5-fold ULN, or chronic active hepatitis or liver function impairment (AST and ALT ≧3-fold ULN).
7. Overt proteinuria (repeat spot urine protein >300mg/dl by dipstick method).
8. Patients are taking cyclosporine.
9. A history of homozygous familial hypercholesterolemia or familial dysbetalipoproteinemia.
10. Patients with alcohol and drug abuse in past 3 years.
11. Serious or unstable medical or psychological conditions.
12. Hypothyroidism (TSH > 5 μIU/mL).
13. In the investigator's opinion, continuation in the study would be detrimental to the patient's well-being or might confound the clinical trial.