We have specifically examined warm and cool sensitivities in 60 diabetic and 43 nondiabetic individuals. Diabetic patients tended to have less warm and cool sensitivity than the control subjects (P less than .001 for age less than 50 yr and P less than .05 for age greater than or equal to 50 yr). Both patients asymptomatic for neuropathy and patients with symptoms had impairment of warm and cool sensitivity (P less than .05 for comparisons with control subjects). These differences persisted (P less than .05) in covariance analyses with age included as a covariate. There was a nonlinear association between warm sensitivity and hemoglobin A1c. Warm-sensitivity values in the lowest and middle tertiles of the hemoglobin A1c distribution were similar; however, warm-sensitivity values of patients in the highest tertile were markedly increased (P less than .05 for the comparison of the highest tertile with the lowest and middle tertiles combined). There tended to be more warm insensitivity than cool insensitivity among the diabetic patients, and this difference increased with worsening glycemia. These data indicate that both warm and cool sensations are markedly impaired in asymptomatic adult diabetic patients. They also suggest that warm sensitivity is more impaired than cool sensitivity, and that this is the result of a stronger association between warm sensitivity and metabolic factors.