Microspheres is a novel drug delivery system which involves entrapment of a drug moiety in a polymeric membrane to alter the release profile of the drug. The present book provides a guide on development and evaluation methodology for microspheres for anticancer drug. Ethyl cellulose microsphere for anticancer drug 5-Flurouracil is selected as a model example. 5-FU is an antimetabolite and immunosuppressive agent. It is used in the treatment of breast, colon, stomach, pancreas, ovary, urinary bladder and lung cancers. But it has a rapid plasma clearance and a short half-life. The drug can be encapsulated in microspheres to prolong its residence time and thereby its action. The ethyl cellulose microspheres containing 5-FU were prepared by a w/o/w emulsification solvent evaporation technique. The process variables in the preparation of 5- FU loaded ethyl-cellulose microspheres were optimized.A factorial design was employed to evaluate the effect of the selected independent variables on some in-vitro attributes of microspheres. Accelerated stability studies of 5- FU loaded ethyl cellulose microspheres was performed.