Geometry and electronic structure of the rhombohedral C, polymer are studied by means of density-functional theory (DFT) within the local-density-approximation (LDA). It is found that stacking sequence proposed by Chen et al. is more stable than the original model by Nunez-Regueiro et al., although the energy difference between the two is very small. The material is a semiconductor with the LDA gap of 0.68 eV. Conduction bands show dependence on the way of stacking, and density of states has a sharp peak at the conduction bottom. Bond lengths are also calculated and found to be in good agreement with the results of the X-ray structure analysis. (C) 2003 Published by Elsevier B.V.