RP-8 is one of several mRNAs elevated during apoptosis in immature thymocytes. We used in situ hybridization to look for RP-8 mRNA in the cerebella of weaver mice. In the weaver mouse cerebellar granule cells fail to differentiate and instead die during the first two weeks of postnatal development [30]. We demonstrate that the dying cells exhibit DNA degradation, a characteristic feature of apoptosis. RP-8 is expressed in the weaver cerebellum during the period of granule cell death, and is limited to cells in the same region where apoptotic granule cells are located. Thus, RP-8 expression, first associated with PCD in thymocytes, correlates with granule cell death in the weaver cerebellum.