Antihypertensive agents are used to prevent morbidity and mortality related to hypertension. Prescribing patterns and the cost of some antihypertensive were studied for 600 patients attending medical clinics in four private hospitals in Dar es Salaam using the WHO drug use indicator forms. The average number of drugs per prescription ranged from 1.9 to 4.2 while that of antihypertensives varied from 1.3 to 2.1. About 50 % of the prescriptions contained 2 to 3 drugs. The most frequently prescribed antihypertensives were diuretics (41 %), β-blockers (28.5 %), calcium channel blockers (19.8 %), hydralazine/losartan (18.5 %) and angiotensin converting enzyme inhibitors (11.5 %). Antihypertensives prescribed as monotherapy included atenolol (23.2 %), bendrofluazide (22 %), frusemide (19 %), hydralazine (11.2 %), nifedipine (9.8 %), amlodipine (9.5 %) and enalapril (9.3 %). Among the combination therapy drugs were angiotensin converting enzyme inhibitor+diuretic (7 %), β-blocker+diuretic (4 %), calcium channel blocker+losartan (2.3 %), β-blocker+angiotensin converting enzyme inhibitor (2.2 %), calcium channel blocker+angiotensin converting enzyme inhibitor (1.8 %) and diuretic+hydralazine (1.7 %). The cost of nifedipine, bendrofluazide and frusemide was about five to six times higher in the private hospitals than at the government owned medical stores department. This study reveals a need for continuing education and standard treatment guidelines for rational prescribing of antihypertensive drugs.