A computer accessible catalogue of submillimeter, millimeter, and microwave spectral lines in the frequency range between 0 and 3000 GHz has been developed. The information listed for each spectral line includes the frequency and its estimated error, the intensity, lower state energy, and quantum number assignment. The catalogue has been constructed by using theoretical least squares fits of published spectral lines to accepted molecular models. The catalogue currently contains over 90,000 lines of 133 atomic and molecular species.