This cross-sectional study aimed to determine the relationships among large, small, and autonomic fiber neurophysiological measures in patients with diabetes. The study included 130 individuals: 25 healthy subjects and 105 diabetic subjects, classified by the presence or absence of neuropathy. All subjects underwent various neurophysiological tests, including autonomic testing, nerve conduction studies, quantitative sensory testing, and nerve-axon reflex vasodilation. The results showed that neurophysiological tests were abnormal in patients with clinical evidence of diabetic neuropathy compared to healthy controls and those without neuropathy. Correlations among individual tests varied widely, both within and between test groups. A two-step hierarchical cluster analysis revealed that neurophysiological tests do not aggregate by typical nerve fiber subtypes. The study concluded that different testing modalities measure distinct neurophysiological parameters and are not interchangeable. However, only a small number of neurophysiological tests are required to clinically differentiate individuals with neuropathy from those without. The natural clustering of both patients and healthy controls suggests that variations in the population will need to be considered in future studies of diabetic neuropathy.This cross-sectional study aimed to determine the relationships among large, small, and autonomic fiber neurophysiological measures in patients with diabetes. The study included 130 individuals: 25 healthy subjects and 105 diabetic subjects, classified by the presence or absence of neuropathy. All subjects underwent various neurophysiological tests, including autonomic testing, nerve conduction studies, quantitative sensory testing, and nerve-axon reflex vasodilation. The results showed that neurophysiological tests were abnormal in patients with clinical evidence of diabetic neuropathy compared to healthy controls and those without neuropathy. Correlations among individual tests varied widely, both within and between test groups. A two-step hierarchical cluster analysis revealed that neurophysiological tests do not aggregate by typical nerve fiber subtypes. The study concluded that different testing modalities measure distinct neurophysiological parameters and are not interchangeable. However, only a small number of neurophysiological tests are required to clinically differentiate individuals with neuropathy from those without. The natural clustering of both patients and healthy controls suggests that variations in the population will need to be considered in future studies of diabetic neuropathy.