OBJECTIVES: To evaluate prescription of guidelines recommended Angiotensin converting enzyme inhibitors (ACE inhibitors) to established diabetic hypertensive patients, and factors associated with prescription of ACE inhibitors and hypertension control. METHODS: This was a cross sectional study conducted at Penang hospital. Prescriptions written to enrolled 250 established diabetic hypertensive patients were noted on visit 1 along with demographic and clinical data. Implicit review of the patients’ medical record was conducted to find acceptable rationale for non prescription of ACE inhibitors. The enrolled patients were followed for another one visit and their blood pressure (BP) readings noted on visit 2 were related to prescriptions written on visit 1. Data was analyzed by SPSS 16. RESULTS: Two hundred twenty five (86%) patients had multiple comorbidities. The most prevalent comorbidity was cardiovascular disease (55.6%). Two hundred sixteen patients (86.4%) were on polytherapy. ACE inhibitors were the most commonly prescribed antihypertensive agents, prescribed to 158 (63.2%) patients followed by Beta blockers prescribed to 154 (61.6%) patients. Ninety-two (36.8%) patients were not on ACE inhibitors, among whom only 8 (8.6%) had contraindications to its use, and 12 (13%) had diabetic nephropathy and were on guidelines recommended Angiotensin receptor blockers. Chronic kidney disease had statistically significant weak negative association with prescription of ACE inhibitors (Φ=-0.13, P=0.03). One hundred nine (43.6%) patients were on goal BP on visit 2. Hypertension control had statistically significant moderate positive association with the use of ACE inhibitors (Φ=0.26, P<0.01), and weak positive association with use of Aldosterone antagonists (Φ=0.13, P=0.04), polytherapy (Φ=0.17, P<0.01), cardiovascular disease (Φ=0.13, P=0.03) and male gender (Φ=0.13, P=0.03). CONCLUSIONS: Despite of guidelines recommendations and positive effect of ACE inhibitors on hypertension control, the use of ACE inhibitors in hypertensive patients suffering from diabetes mellitus was suboptimal at Penang Hospital.