Specially engineered drug particles can solve solubility and formulation problems, which are major challenges for the pharmaceutical industry. Ultrasound irradiation induces acoustic streaming, and highly localized temperature and pressure within the fluid, which can lead to a reduction in crystal size and the inhibition of agglomeration. This study covers properties inherent to particle engineering as well as methods for microparticle production and characterization. Melt emulsification and solvent diffusion using ultrasound to complete with drying are presented on the example of poorly water-soluble Gemfibrozil. Differences in particle size were found depending on the processing parameters applied. During structural characterizations, strong interactions were detected between the drug and the stabilizers. Amorphous or crystalline Gemfibrozil could be obtained.