We have examined the use of successive stimulated Raman adiabatic passage (STIRAP) excitations to control the isomerization reaction HCN --> CNH. We show that this method generates virtually complete transfer from an arbitrary initial vibrational state of HCN to an arbitrary final vibrational state of CNH. This result is valid even in the presence of a substantial number of background states that have non-zero dipole transition moments among themselves and with the subset of STIRAP states, and when pairs of background states are in resonance with the applied field.