The vascular response of the skin was evaluated by transcutaneous oximetry (TcPO2) in the forearm in 119 adolescents with type I diabetes aged 10.4-19.8 (median 15.3) years, with a duration of diabetes 0.7 to 18.3 (median 7.8) years, and 49 nondiabetic adolescents aged 11.3-18.8 (median 15.5) years. Two different vascular stimuli were used: heating of the probe to 43 degrees C and 5 min of ischemia. Baseline TcPO2 after 13 min of equilibration at a probe temperature of 43 degrees C, postischemic maximum TcPO2, and the postischemic TcPO2 increase were significantly lower in the diabetic group compared to the control group (p = 0.0001, p < 0.0001, and p = 0.0001, respectively). In both the diabetic and the control groups, gender differences were found for baseline TcPO2 (p = 0.0001 and p = 0.0009, respectively) and postischemic maximum TcPO2 (p = 0.0001 and p = 0.005, respectively), the girls having consistently higher values. After controlling for gender by multiple linear regression analysis, duration of diabetes showed a significant effect on postischemic maximum TcPO2 (R2 = 22%, p = 0.02). The postischemic TcPO2 increase was not affected by gender. Lower values for the postischemic TcPO2 increase were related to higher GHb values (R2 = 4%, p = 0.03). Abnormal values for oximetry were associated only with some autonomic nerve function abnormalities. Differences in the vascular response to heat and ischemia as measured by transcutaneous oximetry can be demonstrated between adolescents with type I diabetes and nondiabetic controls, as well as between girls and boys. Lower values in diabetic subjects are weakly associated with diabetes duration and metabolic control, independent of gender.