Microspheres are characteristically free flowing powders consisting of proteins or synthetic polymers having a particle size ranging from 1-1000 μm. The range of Techniques for the preparation of microspheres offers a Variety of opportunities to control aspects of drug administration and enhance the therapeutic efficacy of a given drug. Microspheric drug delivery system has gained enormous attention due to its wide range of application as it covers targeting the drug to particular site to imaging and helping the diagnostic features. It also has advantage over liposome as it is physicochemical more stable. Microsphere is a new design of controlled drug delivery system should primarily be aimed achieving more predictable & increased bioavailability of drug, Accurate delivery of small quantities of potent drugs, Protection of labile compounds before and after administration and prior Reduced drug concentrations at sites other than the target organ or tissue, Longer duration of action, etc. It also has advantage over various other dosage forms like we know for lungs disease now a days aerolised drugs are used for local delivery of drugs but it has disadvantage of shorter duration of action so for sustained release and reducing side effects and hence to achieve better patient compliance microspheres can be used. Moreover the microspheres are of micron size so they can easily fit into various capillary beds which are also having micron size.