Local anesthetics containing biodegradable polyester microparticles are prepared using a modified solvent-evaporation process and a spray drying technique. The preparation methods are compared critically. The modified solvent-evaporation process is preferred for the preparation of microparticles. Yields of 90% and microparticle size distributions can be influenced in a reproducible manner. Using the spray drying technique yields are only 60%. The product is characterized by a high portion of microparticles under 10 microns, which are responsible for the rapid release of cinchocain in 168 h as well.