Sural nerve biopsy may, in selected cases, give valuable information in the investigation of patients with polyneuropathy. The prevalence and severity of patient discomfort after fascicular nerve biopsy was investigated in 67 patients by a mailed questionnaire. A lasting (greater than 6 months) significant discomfort was found in 6 patients (11%), in 3 of these the symptoms were graded as severe. Thus, sural nerve biopsy should be limited to cases in which important information may be expected and the patients should be carefully informed of the risks of long-lasting discomfort.