The common peroneal nerves of 15 male rats were severed and the rats were divided into four groups: immediate grafting (I group); grafting delayed one month (IM group); grafting delayed for three months (3M group) and 5 healthy rats were used as controls (control group). All the rats were sacrificed 5 months after grafting. Three morphological indices of the myelinated axons were evaluated, the mean number per unit area, their mean diameter and the axon packing density. The sites examined were, the proximal stump of the recipient nerve, the grafted nerve and the distal stump of the recipient nerve. When repair was carried out late there was atrophy of the axons within the proximal stump, indicating that delay affected axon regeneration as well as resulting in reduced activity in the distal stump. The "3M" group showed poor regeneration in comparison to the "I" group. However, in the "IM" group, the regeneration rate was similar to that of the "IM" group. Our results indicate that early secondary grafting should be considered when circumstances exist which make primary repair undesirable.