We present a model of circular dichroism for proteins that is based on the classical electromagnetic theory for optical activity. The two additional constituents of the model are as follows: an appropriate characterization of the secondary structure of the protein residues and the assignment of an effective polarizability to each type of classified residue. The set of effective polarizabilities is obtained by means of a Monte Carlo statistical method, which is used to analyze a series of synchrotron radiation circular dichroism spectra together with their corresponding crystallographic structures. As a result, the predicted spectra from our model are in good accord with experimental data, as well as with the results of some other theoretical approaches.