The hepatic removal of BSP from the blood during continuous intravenous infusion was calculated. The technic adopted in these researches has achieved results which complete and partly modify previously published conclusions. By using very variable rates of infusion, the existence of two different patterns could be demonstrated. The first involves the mechanism of removal of BSP from the blood when the rate of infusion is less than 25 mg. per minute, in normal subjects. In these circumstances the rate of removal is strictly correlated with the dose infused. When the rate of infusion is more than 25 mg. per minute, the rate of removal does not increase further. The removal rate thus obtained, which is usually not greater than 20 mg. per minute, therefore expresses a maximal capacity which, from the findings of the present investigation, can be defined as the “maximal removal capacity” for BSP. The existence of this phenomenon is important for two reasons. In the first place, the hypothesis that the uptake of BSP from the plasma by the liver is due simply to the diffusion of the dye into the liver cells now seems improbable, and an active role of the liver, possibly through a process of conjugation of BSP, seems more likely. In the second place, investigation of the maximal removal capacity represents a quantitative method for determination of the amount of functioning liver tissue.