In this study a rigorous approach to tissue fluorescence is presented, based on the study of tissue fluorescence as an electromagnetic scattering problem. Fluorescence scattered wave is treated by taking a continuous spectrum distribution in a region of frequencies lower and equal to the excitation frequency. The existence of inelastic field components can be considered as a result of the particular form, that the polarization of the irradiated medium has. In order to provide the most general formulation, the polarization vector P for the observed light frequency (omega) can be written as P(r,(omega) ) equals (omega )(integral) (omega )o d(omega) 'E(r,(omega) ')(tau) ((omega) ,(omega) '), where E(r,(omega) ') is the electric field at the excitation frequency (omega) ' and (tau) ((omega) ,(omega) ') the transfer permittivity function from (omega) ' at the spatial point r, to the emission frequency (omega) , measured at the same point. Substitution of the polarization vector into the electromagnetic field equations leads to a formulation of the inelastic field components. The model used is based on considering tissue as a single dielectric layer, under pulse excitation. The theoretical background for such an evaluation, together with the mathematical technique used and the theoretical results, are presented.