In this paper we apply the Cauchy method to interpolate/extrapolate the Radar Cross Section (RCS) data (amplitude-only data) over a frequency band. This is accomplished by approximating the amplitude-only RCS data by a ratio of two polynomials, the coefficients of which are calculated by using the total least square (TLS) implementation of a Singular Value Decomposition (SVD) technique so as to properly estimate the dimension of the null space. By applying the Cauchy method, an electromagnetic system is represented by a set of poles and zeros in the s-plane. Once these coefficients in the numerator and the denominator polynomials in the Cauchy method are computed using the amplitude-only RCS data, the response can be interpolated/extrapolated over other frequencies of interest. Numerical examples are presented to illustrate the applicability of the Cauchy method in interpolating/extrapolating RCS data over a frequency band.