Dissipative particle dynamics (DPD) simulation is used in this work to model the distribution of ibuprofen molecules in the carrier of solid lipid microparticles (SLM). It is shown from DPD simulation that the aggregating morphology of SLM is different at different oil content levels. At lower oil contents, the oil phase aggregates as spherical particles, while, columnar structure and lamellar structure are observed at higher oil contents. For SLM made from tristearin, ibuprofen molecules are adsorbed on the surface of the carrier. For glyceryl behenate SLM, ibuprofen molecules are distributed in the outer area of the carrier matrix. In cetyl alcohol SLM, however, part of the ibuprofen molecules locate at the outer area of the carrier matrix, while the remaining is distributed in the inner area of the matrix. The mesoscale simulation results are satisfactorily verified by the in vitro experiments and tests. For the three SLM, an initial burst release happens since ibuprofen molecules locate at the surface or the outer area of the carrier matrixes. While the extent of burst release is much reduced in glyceryl behenate SLM and cetyl alcohol SLM for ibuprofen molecules are distributed in the carrier matrixes. (c) 2006 Elsevier B.V. All rights reserved.