This is the first known report of the mapping of precipitation echoes by an airborne synthetic aperture radar (SAR). The detection and mapping of precipitation by an SAR are complicated by the incoherency of the echoes. This limits the effective signal integration time and the attainable size of the aperture. Observations made with a 3.1-cm SAR with a wide vertical side-looking beam flying above a stratiform storm closely resemble earlier vertical cross sections obtained with conventional radar showing snow trails, the bright band, and rain. However, the actual volume sampled by filtering for zero Doppler is displaced slightly to the up-relative wind (upwind in relation to aircraft) side of the vertical plane along the aircraft track, the more so, the faster the particle fall speeds. A true vertical section requires filtering for Doppler velocities corresponding to the fall speeds. Knowledge of the relative winds and fall speeds permits the generation of isodops in the plane normal to the aircraft and the synthesis of either horizontal or vertical cross sections displaced from the aircraft position. Qualitative information about the relative winds may be deduced from the variation of the bounds of the Doppler spectrum with range. Quantitative wind determination is restricted to well-horizontal layers such as the bright band and echo tops.