Gas filled microbubbles are well known as ultrasound contrast agents for medical ultrasound imaging and for non-invasive delivery of drugs and genes to different tissues. Microbubbles designate air or gas filled microspheres suspended in a liquid carrier phase which generally results from the introduction of air or gas. The liquid phase contains surfactants to control the surface properties as well as stability of the bubble. Microbubbles are manufactured from biocompatible materials, so they can be injected intravenously. Microbubbles have an average size (1-8 µm) less than that of RBC's i.e. they are capable of penetrating even into the smallest blood capillaries & releasing drugs or genes, incorporated on their surface, under the action of ultrasound. Ultrasound radiation are used which are non hazardous. Most of the physicians today prefer imaging with ultrasound in combination with microbubbles compared to other diagnostic techniques for low cost and rapidity. The ultrasonic field can be focused at the target tissues and organs; thus, selectivity of the treatment can be improved, reducing undesirable side effects. Recently, targeting ligands are attached to the surface of the microbubbles, which have been widely used in cardiovascular system, tumour diagnosis and therapy. This review focuses on the characteristics of microbubbles that give them therapeutic properties and some important aspects of ultrasound parameters that are known to influence microbubble-mediated drug delivery. In addition, current studies involve discussion of novel therapeutical application of microbubbles.