An instrument is described that operates as a true monostatic reflectometer. The instrument collects complete polarimetric information as well as reflectance. A beamsplitter at 45° to the incident and reflected beam allows monostatic operation. Complete polarimetric information in the form of Mueller matrices are measured by using a polarization state generator prior to the sample and a polarization state analyzer after reflection from the sample and beamsplitter. This Mueller matrix polarimeter is in the dual rotating retarder configuration. Two lasers currently serve as sources. The hardware and data reduction methods are discussed, and measurement results are given.