Hyperbranched polymers, dendritic macromolecules with branch-on-branch structures, have become an important polymer class since the early 1990s. They combine several advantages of the perfectly branched dendrimers with easy accessibility, typically in a one-step synthesis. Hyperbranched polyethers are a particularly interesting class of chemically stable and often biocompatible materials. Multifunctional hyperbranched polyethers with controllable molar mass and comparably low polydispersities can been prepared using hydroxyl-functional epoxides or oxetanes for polymerization via anionic and cationic polymerization mechanisms. Here, we review the progress in the preparation, characterization, and application of these uniquely versatile aliphatic polyether polyols. Their unusual mechanical, thermal, and solution properties render them useful for a variety of applications, for example, as building blocks for various complex macromolecular architectures or in biomedical applications. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013