Patients with diabetic peripheral neuropathy (DPN) eventually lose their sense of touch, mediated by large Aß nerve fibers. Before this occurs, they lose the sense of warm, cold, and pain, mediated by Ad and C nerve fibers. To improve diagnosis of DPN, we will combine measurement of laser evoked potentials produced by an infrared laser with advanced statistical methods to discover patterns that distinguish patients with DPN from those without neuropathy. Because of potential racial differences and health disparities among Blacks and Whites with DPN, we plan to carry out our study in groups evenly divided between Blacks and Whites.