Area under the curve (AUC)–targeted dosing of carboplatin using either the Cockcroft–Gault formula or the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation to inform kidney function may result in different doses and exposures. Area under the curve (AUC)–targeted dosing of carboplatin using either the Cockcroft–Gault formula or the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation to inform kidney function may result in different doses and exposures. The CKD-EPI equation estimates a body surface area (BSA)–normalized GFR value from assumed steady-state serum creatinine (SCr) and anthropomorphic variables. This estimate is converted to an absolute value using the patient’s BSA. Similarly, the Cockcroft–Gault formula estimates an absolute value for creatinine clearance, which is then used as a surrogate of GFR. The GFR value is imputed into the Calvert equation with a target AUC (often 6 mg/ml per min), which results in a carboplatin dose to be administered to the patient. On the basis of the true carboplatin clearance of the patient, an exposure is observed. On the basis of a probability of response (green curve) or toxicity (red curve), the exposure and corresponding probability of response and toxicity can be quite different depending on the kidney function estimate used and the corresponding carboplatin dose administered. Morgan A. Casal et al. CJASN 2019;14:587-595 ©2019 by American Society of Nephrology