Coronary heart disease (CHD) is one of the major causes of death in Hong Kong. Medical non-compliance for patients receiving statin therapy can cause sub-optimal control of serum low-density lipoprotein (LDL) cholesterol and subsequently lead to cardiovascular events. OBJECTIVE: To examine the association of variable patient compliance with statins to the control of serum LDL. METHODS: A 6-month prospective observational cohort study was conducted at the outpatient clinics of a public teaching hospital in Hong Kong. Patients with a 10-year risk for CHD > 20% or CHD risk equivalents who had been initiated on statin monotherapy for < 12 months were recruited. The statin prescription was dispensed to study patients in a bottle with the Medication Event Monitoring System (MEMS) to record the date and time the bottle cap was removed and replaced. Lipid profiles were obtained at baseline and two follow-up visits at month 3 and month 6. RESULTS: A total of 82 patients were recruited and 60.1% were male (mean age = 60 ± 12.3 years). Duration of statin treatment prior to study was 6.9 ± 3.2 months. Baseline LDL prior to statin therapy was 3.8 ± 0.71 mmol/L. Interim findings showed that LDL was reduced by 39 ± 14.2% with 84 ± 20% compliance measured as days with correct dosing at month 3. Significant linear relationship was shown between LDL reduction and days with correct dosing (R = 0.4848, p = 0.0015), dose count (R = 0.4535, p = 0.002) but not timing of dose (R = 0.4959, p = 0.09). A 30% reduction in serum LDL was corresponded to 80% compliance (days with correct dosing). CONCLUSION: LDL reduction was correlated with compliance to statin, and 30% LDL reduction appeared to be achieved at 80% compliance with the prescribed statin therapy.