Abstract: The Z-buffer shadow algorithm is a popular method for producing hard shadows. However, antialiasing of the shadow edges is necessary. This paper provides a new technique for antialiasing of shadow edges that is based on the A-buffer hidden-surface algorithm, which uses bitmasks to describe the area of a pixel occupied by an object. Compared to percentage-closer filtering, which is the standard method for antialiasing shadow edges, the new technique is much faster and has no noisiness present in the blurred regions.