We report results from 120 (25- to 34-year-old) participants in a neuropathy substudy of subjects with insulin-dependent diabetes mellitus (IDDM) taking part in a cohort follow-up study. Diabetic neuropathy was evaluated by quantitative sensory testing, nerve conduction studies, and clinical examination. Mean quantitative sensory thresholds differed significantly by clinical category of abnormal sensation and ankle reflex activity. Mean sural and peroneal amplitudes and conduction velocities were also significantly lower for subjects classified as having abnormal ankle reflex activity. Modeling potential correlates in logistic analyses showed glycemic control, triglyceride levels, and hypertension status to be independently associated with clinically overt neuropathy. Similar lipid and hemodynamic parameters were associated with abnormality by any single assessment method used to define neuropathy. Although follow-up is needed to resolve the best assessment methods for determining neuropathy, these results suggest that good glycemic control as well as control of blood pressure and lipids is advisable.