A way was devised to locate the projection fields (barrels) of the whiskers in fresh neocortex of rats and mice. The cortex was quickly removed and flattened prior to fixation and staining for cytochrome oxidase. The barrels were mapped in relation to the flattened cortex by superimposing specimen and vascular outlines. The topographic location of the barrel field is consistent in rats and in mice. Simple templates were made by xerography on transparency film. Templates were used to accurately excise the barrel cortex of SmI from cortex or to place in vitro injections of HRP. The approach could be generalized to locate other cortical areas from lissencephalic brains.