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A time-domain inverse scattering technique for estimating the parameters of Lorentz dispersive scatterers is proposed. The estimation of the optical and the static relative permittivity, the resonant frequency, and the damping factor of the scatterer is based on the minimization of a cost function. The latter describes the discrepancy between measured and estimated values of the electric field obtained around the scatterer domain when it is illuminated by wideband excitations. The Fréchet derivatives of the cost function with respect to the scatterer properties are derived analytically. These derivatives can be utilized by any gradient-based optimization algorithm, while in the present work, the Polak-Ribière optimization algorithm has been utilized. Numerical results related to the reconstruction of layered Lorentz media show the efficiency of the proposed method.