An instrument is presented that combines the functions of a reflectometer, a spectrometer, and a polarimeter. A Fourier transform spectrometer serves as a light source for a dual rotating retarder polarimeter. Operation of the instrument results in measurement of the complete Mueller matrix of a sample in reflection over a wide spectral band. Calibration and error compensation is described. Polarization characteristics of materials in reflection are determined. © 2002 Society of Photo-Optical Instrumentation Engineers.