OBJECTIVE - To determine whether pancreas transplant recipients maintain normal blood glucose levels during physical exercise. RESEARCH DESIGN AND METHODS - We measured serum glucose, insulin, C-peptide, and plasma glucagon levels in six pancreas transplant recipients and six healthy control subjects matched for age, sex, body size, and level of conditioning during 1 h of bicycle exercise at a workload set to achieve 40% of each individual's previously determined peak oxygen consumption (V̇O2). RESULTS - Serum glucose values were not different between control subjects and transplant recipients before the start of exercise (5.0 ± 0.1 and 4.9 ± 0.1 mmol/l, respectively). Serum glucose levels fell slightly but significantly in both recipients and control subjects during exercise. There were no significant differences in glucose levels between the two groups at any time point during exercise, although mean nadir glucose during exercise was slightly lower in transplant recipients compared with control subjects (4.4 ± 0.1 vs.4.8 ± 0.1 mmol/l, P = 0.04). In control subjects, insulin and C-peptide levels fell significantly within 15-30 min of exercise and glucagon levels rose significantly after 60 min of exercise. In transplant recipients, there was a trend for insulin and C-peptide levels to fall and glucagon levels to rise during exercise, although these changes were delayed and were not statistically significant. CONCLUSIONS - No significant abnormalities in blood glucose were detected in pancreas transplant recipients during bicycle exercise at 40% of peak V̇O2 for 1 h. Compared with levels in control subjects, subtle alterations in insulin and glucagon levels may occur in transplant recipients during exercise. However, these alterations do not appear to result in either hyperglycemia or hypoglycemia during light exercise for up to 1 h.