Tests of the High-Energy Transmission Grating Spectrometer (HETGS) for the Advanced X-Ray Astrophysics Facility (AXAF) showed anomalous scattering of monochromatic radiation. The grating resolving power (E/dE) is of the order 1000, but test designed to search for small-angle scattering by the gratings showed events with significant deviations from the dispersed grating orders and concentrated along the dispersion direction. In this paper, we present a general overview of grating scatter as a result of fluctuations in the grating bar geometry. The grating scatter observed at the AXAF-X-Ray Calibration Facility is shown to be consistent with what one expects from scatter due to deviations in the grating bar geometry form perfect bars. For the purposes of modeling, a rectangular bar mode is adopted and bar parameters are deduced via fitting the model to the scattering data. The correlations deduce from this model lead to a simple physical picture of grating bar fluctuations where a small fraction of the bars, e.g., 1 in 200 are leaning.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.