Recent development and methods of designing and optimizing dry powder formulations have extended the therapeutic potential of inhaled dosage forms. Successful drug delivery as indicated by a high and reproducible fine particle fraction, required to achieve the desired therapeutic effect while minimizing potential toxicity, depends on an understanding of the physico-chemical properties of powder blends, their performance and availability of adequate tools to screen and predict their behavior. The scope of this review includes three important perspectives for inhaled drug delivery: (1) Fundamental aspects of interparticulate interactions of pharmaceutical dry powder aerosols at rest and in resuspension; (2) The influences of pharmaceutical processing including milling, mixing, filling and storage, and their influence on powder dispersion; (3) Current strategies for formulation optimization and methods for in vitro aerosolization performance prediction. (C) Koninklijke Brill NV, Leiden, 2011