In the homozygous staggerer(sg/sg)mutant mouse, most of the Purkinje cells (the primary targets for olivocerebellar climbing fibers) are missing or ectopic. In this study, the organization and cell number of the inferior olivary complex insg/sgwere determined and compared to the inferior olive of the wildtype (+ / +) mouse. Our results indicate that there is a marked disorganization and loss of almost 60% of the cells within the inferior olivary complex. This suggests that the inferior olive may be secondarily affected by the staggerer gene due to the defects in its main target cell, the Purkinje cell.