A new oral sustained release formulation containing 20 mg nifedipine (Coral retard) was administered twice daily to 30 patients suffering from coronary diseases and/or hypertension, in order to assess its clinical effectiveness. The controls of blood pressure and pain before, during and after 30 days of treatment revealed a significantly good therapeutic action of the new formulation, both as an antihypertensive and an antianginal remedy. Blood examinations exhibited an optimum tolerability of the test product. Moreover, in 8 additional subjects free of cardiovascular and other diseases, the formulation was compared to a commercial sustained release product in order to evaluate its bioavailability after a single 20 mg dose. The product under study showed a satisfactory bioavailability when compared to the reference product. It is concluded that the new formulation can be successfully applied to the treatment of hypertensive and/or coronary diseases with a considerable simplification of the dosing schedule and an improved patient compliance.