• An F-wave conduction study was performed to determine proximal vs distal slowing of motor nerve conduction in the lower extremities in nine patients with chronic renal failure who were undergoing long-term hemodialysis and in 11 normal control subjects. The values of the F-wave ratio and the difference between the longest and shortest F-wave latencies were significantly longer than the control values in five patients, implying predominant affection of the proximal peroneal nerve segments. In the remaining patients, the proximal and distal peroneal nerve segments were equally affected. The distal motor nerve conduction velocities of the posterior tibial nerves were also reduced, while the values for the median and ulnar nerves were generally within the normal range. It is important to study multiple F-wave characteristics, in addition to the conventional nerve conduction, for complete assessment of peripheral nerve function in these patients.