The rat protein kinase C substrate neurogranin has a granular distribution in cortical and hippocampal neurons. We demonstrate that in these cells, granular labelling corresponds to a local concentration of neurogranin-immunoreactivity at both the membranes of mitochondria and trans-Golgi vesicles and soma-proximal dendritic shaft and spinal head structures. Our findings suggest that the function of neurogranin could be affected by protein assembly at these cellular sites.