Metabolism of very low density lipoprotein-triglyceride (VLDL-TG) was studied in the isolated perfused rat kidney (IPRK). Recirculating perfusate consisted of KrebsHenseleit bicarbonate buffer containing 6% defatted albumin and VLDL-TG which has been labelled in vitro with 14C-tripalmitin. Results show that the IPRK catabolizes VLDL-TG. Renal removal of VLDL-TG from perfusate was impaired in the presence of 1.0 mM palmitate. A lower palmitate concentration, 0.4 mM, was without effect. It is concluded that high concentrations of circulating free fatty acids impair renal metabolism of fatty acids derived from VLDL-TG.