We report high-resolution spectroscopy of 125 field stars previously observed as part of the Sloan Digital Sky Survey and its program for Galactic studies, the Sloan Extension for Galactic Understanding and Exploration (SEGUE). These spectra are used to measure radial velocities and to derive atmospheric parameters, which we compare with those reported by the SEGUE Stellar Parameter Pipeline (SSPP). The SSPP obtains estimates of these quantities based on SDSS ugriz photometry and low-resolution (R ~ 2000) spectroscopy. For F- and G-type stars observed with high signal-to-noise ratios (S/Ns), we empirically determine the typical random uncertainties in the radial velocities, effective temperatures, surface gravities, and metallicities delivered by the SSPP to be 2.4 km s-1, 130 K (2.2 %), 0.21 dex, and 0.11 dex, respectively, with systematic uncertainties of a similar magnitude in the effective temperatures and metallicities. We estimate random errors for lower S/N based on numerical simulations. Based on observations obtained with the Hobby-Eberly Telescope (a joint project of the University of Texas at Austin, Pennsylvania State University, Stanford University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen), the W. M. Keck Observatory (operated as a scientific partnership among the California Institute of Technology, the University of California and NASA), and the Subaru Telescope (operated by the National Astronomical Observatory of Japan).