A stereotaxic atlas of the pig brain has been established. It consists of 60 frontal and 18 sagittal drawings illustrating Nissl stained sections. A stereotaxic apparatus adapted for the Pig was used to determine the brain coordinates. Radiographic techniques were applied to verify the correct position of the central nervous structures in the apparatus. The zero horizontal plane contains the line joining the recessus preopticus and the posterior commissure (PC) images. These two landmarks were identified by ventriculography. The anterior limit of the PC is used as zero on the stereotaxic atlas. Vertical electrode trajectories implanted at a fixed depth in the brain and at different anterior and lateral levels were used to determine the lateral, vertical and height coordinates in the different planes. Then the brains were perfused and embedded to avoid major displacement of the cerebral structures. Frontal and sagittal serial sections of 100 microns were performed in two different animals. Magnified diagrams of brain sections representing the cellular architecture of the brain structures were produced, some of which are illustrated with photomicrographs. For certain areas, the limits of the nuclei were difficult to determine even when complementary electrophysiological studies were carried out. Each plate is accompanied by a list of abbreviations used to label structures on the plate, together with the terms which they represent. This work should provide a useful anatomical guide for research on the pig brain.