Nondestructive three-dimensional refractive-index measurements are used for the determination of both crystallinity and orientation in thin polymer films. The prism waveguide coupler is particularly suitable for three-dimensional isotropic and anisotropic thin-film studies because of the quantitative character of the information obtained and the ease of data acquisition. It has been limited, however, to measuring the refractive index of optically transparent or weakly absorbing films. This study shows that a modified prism waveguide coupler can be used to determine the complex refractive index over a range from transparent to highly absorbing films from the internally reflected light intensity, Thus, both the refractive index, n, and the extinction coefficient, k, can be obtained. This method is used to determine the anisotropic three-dimensional n and k values of spin-coated emeraldine base and hydrogen chloride doped emeraldine salt polyaniline films.