Few studies have addressed the profile of adherence among ethnic Chinese patients. This study evaluated the factors associated with adherence with angiotensin-converting enzyme inhibitors (ACEIs), an increasingly common antihypertensive drug of choice. The authors included all adult patients who were prescribed an ACEI and paid at least 2 consecutive visits to any primary care clinics of one large territory of Hong Kong from January 2004 to June 2007. The determinants of good adherence to ACEI, as defined by a medication possession ratio > or = 80%, were evaluated by multivariate regression analysis. From 6408 eligible patients, 88.0% were adherent. Patients attending family medicine specialist clinics (adjusted odds ratio [AOR] = 1.46, 95% confidence interval [CI]: 1.12-1.91, P = .005) and follow-up visitors (AOR = 2.98, 95% CI: 2.49-3.55, P < .001) were significantly more likely and attendees of staff clinics (AOR = 0.48, 95% CI: 0.25-0.94, P = .033) were less likely to be adherent to ACEIs. Patients' age, gender, socioeconomic status, district of residence, and the number of comorbidities were not found to be associated with good adherence. Adherence-enhancing strategies should therefore be particularly focused on the new visitors (likely to be drug naive), and future research directions should delineate the best health service setting that could facilitate adherence to ACEIs.