Objective: Double peak sensory responses elicited with submaximal stimulation is an electrophysiological method that has not been studied previously in pathological conditions. The second peak of the response was claimed to be produced by anodal stimulation and originated from the most distal regions of the nerve fibers. The objective of the study was to test double peak sensory responses in two groups of diabetic patients in two different stages of the disease. Methods: Conventional nerve conduction studies performed in 20 patients with impaired glucose tolerance (IGT), 14 with type 2 diabetes mellitus (DM), and in 25 healthy control subjects revealed normal results. Orthodromic double peak sensory responses with submaximal stimulation of the median nerve, sural/radial amplitude ratio and medial plantar nerve orthodromic sensory nerve action potentials (SNAP) were also studied in the non-dominant side. IGT and DM patients were evaluated with the Michigan Diabetic Neuropathy Scale (MDNS). Results: The mean median nerve sensory distal latency was prolonged and ulnar SNAP amplitude was significantly reduced in DM patients compared to the subjects in the other two groups. DM and IGT patients had higher stimulation thresholds and maximal stimulation intensities than the control subjects. The latencies of the first and second components of the double peak sensory responses were also prolonged in the DM group compared to the other groups. Conclusion: This study did not reveal any result indicating that double peak sensory responses with submaximal stimulation were superior to conventional nerve conduction studies in the detection of early diabetic polyneuropathy. However, the number of subjects included in our study is insufficient for a final decision on this matter, and further studies are needed to include diabetic patients having clinical signs and symptoms of polyneuropathy and normal nerve conduction studies. Stimulation threshold assessment might be a promising tool for the detection of early nerve involvement, if its reproducibility is achieved. This study showed once more that peripheral neuropathy may develop in individuals with diabetes even in early stage and with good glycemic control. (Archives of Neuropsychiatry 2010; 47: 338-43)