PROBLEM TO BE SOLVED : To provide a method for producing nanoparticles and/or microparticles of a biologically active material with powder handling characteristics superior to powders made by conventional size reduction processes. SOLUTION : The method comprises the steps of : dry-milling a solid biologically active material and a millable grinding matrix in a mill for a time period sufficient to produce particles of the biologically active material dispersed in an at least partially milled grinding material. SELECTED DRAWING : None COPYRIGHT : (C)2019, JPO&INPIT