In this paper a comprehensive full-wave analysis of the double-sided or bilateral microslotline both in its single slot and coupled slots configuration, is presented. First, an equivalent model of the original structure is derived upon which a variational method is applied for establishing a stationary expression for the line's dominant mode propagation constant. The electric field in the slot(s) is the trial quantity and suitable approximations of its distribution are made which are also used for calculating the characteristic impedance. Numerical results are presented for the single and for the first time for the coupled slot(s) configuration.