Multiple sclerosis (MS) is a disorder of the central nervous system (CNS). It is characterized by episodic and progressive neurological dysfunction resulting from inflammatory and autoimmune reactions, myelin loss, conduction block, oligodendrocyte pathology, gliosis, and axonal loss in CNS. Recent years have witnessed advances in better understanding the immune pathogenesis of MS, prompted by animal models, human pathological observations and MRI studies. There have been significant changes in the therapeutic regimens in MS, with an emphasis on preventative treatment of an ongoing disease process. Agents in use and in the research pipeline have mechanisms that act on various anti-inflammatory and immunomodulatory properties, including blocking leukocyte migration into CNS and targeting chemoattraction. In addition, recent studies on the neurodegenerative components of MS have directed therapeutic trials to neuroprotection and neurorestoration. In this paper, we summarize the current understanding of the mechanisms of approved pharmacological agents and review the putative mechanisms and status of some important agents in clinical phase two or three trials in MS.