The gross anatomical distribution of an antigen is typically mapped using a combination of serial sectioning, immunocytochemistry, and three-dimensional reconstruction. This is a tedious and time-consuming procedure, which introduces an array of potential alignment and differential shrinkage errors and requires considerable experience and specialized equipment. In particular, it is unsuited for routine screening applications. To circumvent these problems, this unit presents a routine whole-mount immunocytochemistry protocol that can be used to map many antigenic distributions in the developing and adult brain. The technique can also be easily adapted to detect anterograde and retrograde transport tracers.