This paper presents an alternative procedure for obtaining the ABCD matrix of a generic multiphase transmission line. The ABCD matrix is obtained from the open and short-circuit responses of the line calculated in the frequency domain. The proposed procedure was used to obtain the ABCD matrix of a typical 440 kV overhead three-phase transmission line. To ensure that the proposed procedure was developed correctly, the ABCD matrix was used to represent the transmission line in simulations of electromagnetic transients resulting from switching and lightning. These simulations were also carried out with two known models that yielded identical results. The comparisons showed that the proposed methodology was developed correctly and that its main advantage is that it can be applied to generic multiphase transmission lines, whereas the existing methodology in the literature is restricted to three-phase lines with vertical planes of symmetry.