Pathophysiology and pathoanatomy of uremic neuropathy are not yet well understood. A single hemodialysis positively increases nerve conduction velocities of uremic patients, thus demonstrating a functional A alpha-fiber improvement by detoxification. This study tested whether non-invasive Vibrameter and Thermotest studies show a similarly positive effect for A beta-, A delta- and C-fibers and whether the psychophysical techniques might substitute for nerve conduction studies. 20 uremic patients depending on chronic intermittent hemodialysis were examined shortly before and after a hemodialysis. Using a scaled 128 Hz tuning fork, a Vibrameter and a "Marstock"-Thermotest, vibratory and warm and cold thresholds were assessed at both internal malleoli according to the method of limits. In addition, thermal thresholds were determined at the volar aspect of the non-shunted wrist. In nine patients the Vibrameter showed elevated thresholds before and after dialysis as did six patients with the tuning fork. Warm or cold thresholds were abnormal in four patients before treatment and in eight patients after dialysis. This was due to some patients reporting elevated thresholds after dialysis although they had had normal thresholds before the treatment. Still, the overall sum of abnormal thermal or vibratory thresholds at the different tested body sites had decreased after treatment. Moreover, mean values of thermal and vibratory thresholds of the 20 patients improved with dialysis (p < 0.05). Tuning fork results were too coarse and failed to show a dialysis effect.(ABSTRACT TRUNCATED AT 250 WORDS)