The nucleus of the posterior commissure projects to the intermediate (SGI) and deep (SGP) grey layers of the ipsilateral superior colliculus throughout its rostral-caudal dimension. This projection terminates in a patchy, discontinuous, manner. The patches form a tier in the dorsal half of SGI, and are smaller medially than laterally. These results are discussed in relation to other patchy projections to SGI and in relation to a possible modular organization of the superior colliculus.