High-resolution infrared laser spectroscopy has been used to study HCN-H-2 and HCN-D-2 complexes in the gas phase. The experimental results are compared with ab initio calculations that are also reported here. The latter calculations reveal two prominent minima on the potential surface, one corresponding to a "T-shaped" complex with the H-2 at the hydrogen end of the HCN and the other a "linear" complex with the H-2 H-bonded to the nitrogen. The latter minimum is the global minimum on the surface, in agreement with the fact that this structure is observed experimentally for both o-H-2 and p-D-2. <(C)> 2001 American Institute of Physics.