The uptake of chlorine e6 derivatives by peripheral blood leukocytes was studied using a fluorescence-activated sorter. The analysis showed that the order of pigment uptake by leukocyte populations is the following: granulocytes > or = monocytes > lymphocytes. It was found that the accumulation of the pigments in the cell significantly varied. The level of chlorine e6 dimethyl ester accumulated by cells was found to be 15 times higher than that of chlorine e6. It was assumed that the differences in pigment uptake by different types of blood cells are due to structural and morphological features of leukocytes. The data obtained may be useful in developing the new methods of photodynamic therapy.