The structure and electronic properties of copper clusters Cun(n= 2-5, 8 and 13) have been studied through ab initio LCAO–MO–SCF calculations with a Gaussian basis set (12, 7, 5) contracted to [5, 3, 2]. The linear structure is more stable than the two- and three-dimensional structures for n= 3 and 4, but becomes less stable for n 5. Since for Cu8 the band of 3d levels and the 4s levels are well separated and for Cu13 the two bands just begin to overlap, the distribution of energy levels in these clusters appears to be rather different from that in the bulk metal. This is also a consequence of the fact that most of the atoms in the cluster Cu13 are surface atoms. The binding energy increases quasi-linearly with the number of atoms in the cluster up to n= 8.