Voles (Microtinae) are among the smallest of mammals which feed extensively on plant leaf material. They achieve higher digestive efficiencies than large ungulates, and this study considers the role that dentition may play in grinding food into small particles, so assisting efficient digestion. Bank (Clethrionomys glareolus) and field voles (Microtus agrestis) were found to chew their food into far smaller particles than ungulates, field voles producing smaller particle sizes than bank voles. Scanning electron micrographs showed differences in tooth wear patterns between species, and in bank voles a change in diet led to changes in tooth wear and to changes in the efficiency with which food was processed. Field voles have a pore structure on the occlusal surface of the molar teeth which could play an important role because when the teeth act antagonistically these pores could grate fragments of plant leaves into very small particles and hence enable the animals to achieve high digestive efficiencies.