Vertical excitation energies belonging to some different Rydberg series of hydrogen chloride have been determined with a coupled-cluster theoretical approach. These excitation energies have allowed us to calculate electric dipole transition intensities in HCI and allow additional assessment of the calculation approach presently used to provide an adequate description of the valence and Rydberg states of HCI. The molecular quantum defect orbital has been applied to the calculation of oscillator strengths. In particular, new insight is given on the assignment of states as the R-1 Pi, the (1)Delta(4d pi and 5p pi), the (1)Sigma(+)(4d pi), and the nd delta((1)Pi, (1)Phi) and 4f states.