We have measured the urinary excretion of deoxypyridinium (D-Pyr) crosslinks, a sensitive and specific marker of bone resorption, in morning urine in 102 healthy, nonhospitalized, Caucasian subjects (8-18 years) and in 18 diabetic subjects (12-17 years). The free D-Pyr crosslinks were measured using the Pyrilinks D-Assay. In the diabetic subjects, plasma glucose was regulated throughout the night by a constant infusion of insulin and a variable infusion of 24% glucose. In the nondiabetic subjects, the excretion of D-Pyr increased until 12-14 years of age, and thereafter decreased, and the excretion of D-Pyr/hour was correlated with the height Z-score. The excretion of D-Pyr/hour and the D-Pyr/creatinine ratio was higher in the diabetic adolescents than in the nondiabetic adolescents. In subjects over the age of 12, the D-pyr/creatinine ratio was higher in males than in females. In conclusion, in healthy children and adolescents, the excretion of D-Pyr peaks at 12-14 years of age. The D-Pyr excretion is higher in diabetic than in nondiabetic adolescents, suggesting increased bone resorption in diabetic adolescents.