Seven rats were infused with 14C-labeled Intralipid at a constant rate of 0.38 ml per hour over a time period of 4 hours. Four rats served as controls and received an infusion of 0.15 M NaCl or of serum albumin two hours after the start of the experiment. In these animals the plasma triglyceride concentration rose linearly from 30 to 240 min and paralleled the total blood radioactivity. The triglyceride concentrations at the end of the experiments were about 25 times as high as at the beginning. Three rats receiving 2 hr after the start an additional infusion of beta 2-glycoprotein-I at a rate of 10 mg per hr showed a markedly enhanced triglyceride removal from the plasma, reaching a steady state which lasted for more than 30 min. It is concluded that beta 2-glycoprotein-I affects the triglyceride clearance under these experimental conditions.