A recent clinical trial in patients with chronic kidney disease (CKD) and diabetic nephropathy demonstrated that bardoxolone methyl (CDDO-ME) increases estimated glomerular filtration rate (eGFR) by an unknown mechanism. The paper by Ding et al. suggests that short-term administration of a CDDO-ME analog increases GFR by increasing glomerular surface area. However, changes in other renal hemodynamic parameters cannot be excluded. Vigorous testing of CDDO-ME and highly purified analogs is warranted to determine their physiology, pharmacology, and efficacy and to exclude serious side effects.