The test formulation of controlled release diltiazem pellets was evaluated in vivo, in comparison with Herbesser SR. Six healthy volunteers participated in the study, conducted according to a randomized, two-way crossover study design. The preparations were compared using the pharmacokinetic parameters plasma concentration-time curve (AUC(0- infinity)), peak plasma concentration (Cmax) and time to reach maximum plasma concentration (Tmax) were estimated from the plasma concentration-time profiles for each volunteer. The test formulation was found to be comparable with the Herbesser SR in the extent of bioavailability but differ in the rate of absorption, the test formulation being less sustained. No lag time was observed in any of the volunteers indicating that both formulations started to release their drug content immediately upon rupture of the capsule but in sustained manner. Moreover, the values of pharmacokinetic parameters obtained were comparable to those reported in the literature.