A b s t r a c k A simple method of approximating frequency Characteristics of composites in a form convenient for timedomain numerical modeling is proposed. The frequency characteristics can be obtained from experiment or calculations based ou the Maxwell Garnett mixing formalism. The resultant frequency characteristic might be of a complex shape corresponding to a Combination of a number of absorption peaks. The approximation is made by a series ofDebye-like terms using a genetic algorithm (GA). This leads to the necessity of taking a number of terms in the approximating series. Every term corresponds to its pole, i.e., the frequency where the maximum loss occurs. Some numerical examples are represented.