To observe the histological alterations of single nerve fiber structures after nerve elongation by employing a rabbit peroneal nerve stretching model. 14 rabbits weighing mean 3. 0 kg (2.02-3.31 kg.) were used in the experiment. Two rabbits were used as control when only a sham operation was done (group one, 0% stretch). Acute stretching of the peroneal nerves to elongate them by 10% was done in 6 rabbits (group two, 10% elongation) and by 20% (group three, 20% elongation) in another 6 rabbits. All animals were evaluated by tissue staining technology in a teased-fiber study. The internodal lengths were measured, and nodes of Ranvier and Schmidt-Lanterman notch were observed. The nerve fiber length was increased after stretching. The mean internodal length was 1208.31 microm in group one, 1347.26 microm in group two, and 1411.35 microm in group three. Compared with the control group, mean internodal length was elongated by 11.50% in group two and 16.80% in group three. The difference was statistically significant. The node of Ranvier and Schmidt-Lanterman notch was wider in both group two and group three. Rupture of nerve fiber at the node of Ranvier was observed in group three. The peroneal nerve in rabbits can adapt to mild stretching by internodal length elongation. Elongation by 20% will cause structural rupture and therefore is the limit for nerve elongation.