Azacitidine pharmacokinetic parameters in adolescent patients with renal compromise are not available from the medical literature. We describe a 14-year-old with myelodysplastic syndrome treated with subcutaneous 5-azacitidine for disease relapse 2 years after hematopoietic stem cell transplant. Because of renal compromise, malnutrition, and poor functional status, pharmacokinetic parameters were projected from existing literature data to select the patient's first azacitidine treatment course (1.5 mg/kg/d for 7 d). Posttreatment azacitidine plasma concentrations used to calculate patient-specific pharmacokinetic parameters corroborated initial estimates and systemic exposure associated with therapeutic benefit in adults and permitted individualization of treatment.