Among various polymers, smart polymers have taken much importance in drug delivery systems due to their targeting ability. This review mainly describes the expansion of biodegradable polymers in pharmaceuticals drug delivery that provides mechanism of targeting from both physiological and pathological point of view. Thus, smart polymers due to various actions and responsive drug delivery get more importance in era of novel techniques especially in nanotechnology by formulation of nanoparticles. This progress descends into two categories: i) open loop system that is also known as externally regulated or pulsatile systems, ii) closed loop system that is actually self-regulated systems. External triggers like ultrasonic, magnetic, electric, light and chemical or biochemical agents involved in release of open loop or pulstile drug delivery system whereas self-regulated systems are the systems where controlled variable is detected due to which the system output is adjusted consequently. Several approaches like thermal response, pH-sensitive drug or polymers action, enzyme-substrate reactions are applied for achieving targeted drug delivery systems. The release rate can also be controlled by selection of natural and synthetic nature of smart polymers on the basis of their feedback mechanism. Keywords: Biodegradable, Closed Loop, Open Loop, Novel, Natural, Synthetic and Smart Polymers