Polyolefins are a very important class of commercial polymers in the world today and are used in a wide range of applications. Despite their versatility, they suffer from certain drawbacks that exert a limiting influence on their range of applications. They are nonpolar and therefore exhibit poor hygroscopicity, printability, and dyeability. In addition, they have poor dispersibility with inorganic fillers like talc and mica in composites and poor miscibility in blends and alloys with polar polymers like nylons, polyesters, engineering thermoplastics, and so forth. This restricts their use in several new emerging technologies. One means of overcoming these drawbacks is the introduction of a small amount of polar groups onto the polymer backbone by postpolymerization reactions using the polymer as a substrate. The polar groups impart new properties to the substrate polymer without affecting the backbone properties of the polymer significantly. The objective of this paper is to briefly review some of the published literature in this area.