A new carbon family with prism-C-n (n=3-8, 10, 12, 14, 16, 18, and 20) tube structures has been found by quantum chemical calculations. Periodically and axially piled regular polygons were optimized into the prism-C-n tubes, in which all carbon atoms are equivalent and connected with four single bonds of 0.153-0.161 nm. The relative energies per one carbon atom with respect to graphene are 218-354 kJ mol(-1). The lowest energy barriers of tri[4]prismane and tri[6]prismane with similar prism-tube skeletons were found to be ca. 80 kJ mol(-1), which gives an expectation that carbon skeletons of the prism-C-n tubes are also stable. (C) 2015 Elsevier B.V. All rights reserved.