A canonical ensemble Monte Carlo simulation was performed for Cu2+ in 18.57% aqueous ammonia solution at a temperature of 293.16 K, using ab initio pair potentials and three-body potentials for Cu-H2O-H2O, Cu-H2O-NH3 and Cu-NH3-NH3 interactions. The first solvation shell consists of three water and three ammonia molecules, and the second shell of 11.6 water and 10.2 ammonia molecules. The structure of the solvated ion is discussed in terms of radial distribution functions, coordination number, and angular distributions. (C) 2000 American Institute of Physics. [S0021-9606(00)50109-3].