Collagen microparticles (CMPs) of diameters ranging from about 3 to 40 mu m were prepared by the method of emulsifying and cross-linking native collagen. The particle size was mainly controlled by the molecular weight of the collagen used: an increase in denaturation of the collagen resulted in smaller sizes. Consequently, controlled denaturation is the best method to control the size of CMPs. Total denaturation results in the degradation product gelatin and subsequently yields very small nanoparticles with a minimum diameter of about 0.1 mu m. Collagen microparticles can be used as carriers for lipophilic drugs e.g. retinol, tretinoin, or tetracaine and lidocaine in free base form. Another feature of the biodegradable CMPs is their thermal stability, thus their sterilization can be readily achieved.