Identification of the functions of the genes at system level is one of the greatest challenges in the post genome-sequence era. To reveal functional significance of the genes expressed in the brain, we have been utilizing a comprehensive behavioral test battery on various kinds of genetically-engineered mice. The behavioral test battery covers a broad range of various behavioral domains, such as learning and memory, sensory-motor functions, emotions and motivation. During the past two years, we have assessed behaviors of more than 30 different strains of mutant mice and, surprisingly, we found at least one significant behavioral abnormality in more than 90% of those strains. This fact not only demonstrates that our strategy is useful in elucidating the functions of the genes expressed in the brain but also implies that a large part of the genes expressed in the brain may have some functions. In this workshop, I'd like to introduce some examples of our work using the test battery on mutant mice and to make a proposal to use it as a "hub" for large-scale neuroscience. Establishing a collaborative network among experts in the field would be necessary for greater success of this approach. The potential issues related to implementing such collaborative network or consortium will be also discussed. [J Physiol Sci. 2006;56 Suppl:S51]