We have investigated hexagonal silicon carbide with low dislocation density to reveal inherent dislocation types and structures using the bulk-sensitive synchrotron X-ray topography. This topographic study reveals that: (1) Basal-plane dislocations with the Burgers vector of 1/3 < 1 1 (2) over bar 0 > preferred to be screw dislocations along < 1 1 (2) over bar 0 > in straight shape. (2) Threading dislocations containing the Burgers vector component of < 0 0 0 1 > are mostly mixed dislocations containing that of 1/3 < 1 1 (2) over bar 0 >. (3) Threading edge dislocations with the Burgers vector of 1/3 < 1 1 (2) over bar 0 > are of short lengths, about 30-100 mu m. (4) All these dislocations are connected to convert, combine and dissociate to each other. We discuss the dislocation types and structures in terms of both the Peierls energy and elastic interaction. Moreover, we propose that the source of dislocations with the Burgers vector of 1/3 < 1 1 (2) over bar 0> is due to the propagation from a seed crystal rather than due to the Frank-Read mechanism.(c) 2007 Elsevier B.V. All rights reserved.