Due to the importance of higher carbon oxides of the general formula COx (x > 2) in atmospheric chemistry, isotopic enrichment processes, low-temperature ices in the interstellar medium and in the outer solar system, as well as potential implications to high-energy materials, an overview on higher carbon oxides COx (x = 3-6) is presented. This article reviews recent developments on these transient species. Future challenges and directions of this research field are highlighted. (c) 2008 Elsevier B. V. All rights reserved.