This paper presents an atlas of the rat brain based on horizontal sections stained for acetylcholinesterase (AChE). Fourteen labeled photographs from sections at 0.5 mm intervals are presented. The atlas is intended for use with male rats 250-300 g in weight. It was constructed using the flat-skull position (lambda and bregma in same horizontal plane). Either the interaural midline or bregma can serve as the reference zero point. We have found the stain for AChE to be a useful general purpose stain for identifying brain nuclei and tracts.