A snow reflectance model was developed to assess the bidirectional reflectance distribution function (BRDF) of snow over anisotropic rough surfaces such as fields of sastrugi commonly encountered in some areas of the ice sheets of Antarctica and Greenland. The sastrugi are modeled as regularly spaced identical rectangular protrusions with the same orientation. Interfacet multiple scattering is ignored. Each model sastruga has vertical walls and a small width compared to its length and to its height. The input data for the model are the Sun and the viewing directions, the number of sastrugi per pixel, their dimensions and the bidirectional reflectance for a flat snow surface. The latter is computed by a multiple scattering model, and snow particles are assumed to be spherical (Mie theory). In order to compare the model results with ground measurements acquired at the south pole by Grenfell et al. <1994> and Brandt et al. <1991>, atmospheric effects were taken into account. The model reproduces the global influence of sastrugi on the shape of the BRDF. The influence of sastrugi is clearly visible for zenith viewing angles larger than 50¿. ¿ 1998 American Geophysical Union