The right sciatic nerve of 50 one-month-old male rats was cut under general anaesthesia. Groups of animals were sacrificed at intervals of up to 12 weeks after operation and the length of the femora, tibiae and first and fifth metatarsals were measured with a caliper accurate to 0.05 mm. From the first week, both metatarsals were between 3% and 5% shorter on the denervated side, but there was no further increase of the discrepancy. The femora were less than 1% longer in the denervated limb at the second and eighth week. No difference was found between the lengths of the tibiae. The various factors which could possibly be responsible for these findings are discussed.