The F wave has been thought to be useful for diagnosis of proximal neuropathy such as radiculopathy. But its diagnostic sensitivity is not satisfactory so far, and many techniques were designed to improve the sensitivity. Among these, electronic averaging of F waves were introduced as a simple and useful methods that allow one to quickly summate a large number of F waves, yielding a stable and easily reproducible waveform of shortest latency. We studied the significance of F wave in the diagnosis of lumbosacral radiculo-pathy using both conventional and averaging techniques, and compared their sensitivity. 88 patients were studied who had been diagnosed as lumbosacral radiculopathy by clinical, radiological, and electromyographic findings. The results showed that both conventional and averaging F wave study are not sensitive techniques in the diagnosis of lumbosacral radiculopathy.