A clinical case of L5 radiculopathy with the onset of pain in the lower leg with subsequent addition of pain in the lower back after one month is presented. In the neurological status, hypoaesthesia and decreased muscle strength in the extensor hallucis longus of the left foot were noted. A serial three-fold electroneuromyographic study was performed. When testing the tibial nerve from the abductor hallucis, an A-wave was detected, which was recorded after the F-wave, whereas two months after the onset of the disease, the A-wave disappeared, but the combined duration of the F-wave was increased. Thus, the analysis of electroneuromyographic data in the form of the presence of the A-wave with its localization after the F-wave and an increase in the combined duration of the entire F-wave complex during the study of the tibial nerve in combination with clinical and neuroimaging data is important for the diagnosis of L5 radiculopathy.