Hyperbranched polymers prepared by step-growth polymerization of AB(x) monomers carry a very large number of reactive groups at their numerous chain-ends as well as throughout the macromolecule. These hyperbranched polymers are characterized by very high solubilities and unusually low solution viscosities when compared to linear analogs. This is a result of their globular shape and lack of crystallinity. The preparation and selected properties of two types of hyperbranched polymers, polyphenylene and polyesters, is discussed.