Abstract—The values of the complex permittivity have been determined over the frequency range of 10 MHz to 20 GHz, at 35C using the time-domain reflectometry (TDR) method for 11 different concentrations of each tert-Butyl alcohol [TB] with 2-Propanol [2P] systems. The relaxation in these systems can be described by a single relaxation time using the Debye model [1]. The static dielectric constants for the mixtures is fitted with the modified Bruggeman model by assuming an additional parameter. Different physical parameters are described for the mixture.