Carbamazepine controlled-release tablet formulations containing hydroxypropyl methylcellulose (HPMC) as matrix material at different concentrations were developed and evaluated in vitro and in vivo. The formulation containing 10% HPMC (HPMC-10) showed a controlled-release profile comparable to that of a commercially available, controlled-release carbamazepine preparation (Tegretol(R) CR 200). The kinetics of controlled-release carbamazepine tablets was examined in eight healthy volunteers. The peak plasma concentration of 1.99 +/- 0.56 mu g . ml(-1) was obtained for HPMC-10 at 15.0 +/- 9.0 h, and 1.33 +/- 0.35 mu g . ml(-1) for Tegretol(R) CR 200 at 15.2 +/- 8.9 h, and AUC(0-infinity) values of 85.2 +/- 30.8 mu g . h . ml(-1) and 76.9 +/- 20.7 mu g . h . ml(-1), respectively. Developed formulation (HPMC-10) was found to be bioequivalent to Tegretol(R) CR 200 and, controlled release was obtained with smoother concentration-time curve resulting in less fluctuations.