Objective: An impaired blood flow response is associated with an increased risk of developing decubitus ulcers. This study investigated whether diabetic patients with autonomic neuropathy show an impaired blood flow response following pressure lead, compared with healthy controls. Design: Before-after trial. Setting: University hospital. Patients: Eighteen patients with type I diabetes and autonomic neuropathy, and 15 healthy volunteers. Results: The blood flow response starts with a latency period, followed by a temperature increase (described by the 'time constant'). The blood flow response in both groups showed significant (p < .01) differences. In diabetic patients, the latency time was 312 ± 221sec, the time constant was 339 ± 149sec, and the recovery time was 538 ± 184sec. In controls, latency time was 83 ± 47sec, time constant was 79 ± 69sec, and recovery time was 162 ± 103sec. The velocity of the blood flow response decreased with increasing duration of diabetes mellitus (p = .02). Conclusions: Diabetic patients with autonomic neuropathy show an impaired blood flow response after pressure relief. This finding suggests that these patients have an increased risk of developing decubitus ulcers.