Urinary bladder sensation to ice water instillation was evaluated in 32 patients with diabetes mellitus. Sixteen patients were urodynamically normal (group 1) and the remaining 16 were diagnosed as having diabetic cystopathy (group 2). Eleven out of 16 patients in group 2 could be considered as having impairment of sensation to urinate. Two out of 16 (12.5%) subjects in group 1 could not perceive ice water infusion, whereas 25% of patients in group 2 did not feel the ice water sensation. In group 2, patients with impaired urinary sensation showed relatively high incidence of negative ice water test (36.4%), although there were no statistical differences between the other groups. There was no apparent relationship between prevalence of peripheral neuropathy and that of negative ice water test. Impairment of ice water perception was less frequent than that of mechanoreceptor sensation in patients with diabetic cystopathy.