The postoperative effects of a whole sural nerve biopsy in diabetic (11) and non-diabetic (10 healthy controls, 10 patients with impaired glucose tolerance and 2 patients with polyneuropathy) subjects were investigated by a mailed questionnaire 20-44 months after the surgical procedure (10/11 vs 21/22 answers received). Pain in the biopsy area at follow-up was reported in 4/10 of the diabetic patients (p = 0.01) but in none of the non-diabetic subjects (0/21). An increased number (p = 0.01) of diabetic patients (5/10 vs 1/21) had cold intolerance in their foot or leg whereas 11/31 of all patients had dysaesthesia in the affected skin. Overall 6/31 patients described serious problems at the time of the questionnaire, and 4 of this 6 having diabetes. Loss of sensation was reported in almost all subjects irrespective of diabetes or not; however, a decrease in the area of loss of sensation was reported most often in diabetic patients (8/10 vs 8/21, p = 0.02). It is concluded that whole surval nerve biopsies give rise to persistent problems both in diabetic and non-diabetic subjects. The reason for a sural nerve biopsy has always to be carefully considered before being conducted.