Cellulose acetate butyrate microparticles loaded in carbamazepine were prepared by a solvent evaporation technique. A decrease of the amount of organic solvent (from 80 to 40 mi of methylene chloride) increased the microparticle average diameter (73-111 and 207 mu m) and decreased the carbamazepine release rate (T-50% increased from 33 to 168 and 166.4 min). The microparticle area under the curve at 120 min was similar to that obtained with Tegretol LP(R) 200 tablets.