Leakage kinetics of a fluorescent dye from the interior of a vesicle (or cell) into atl external quencher containing well-stirred medium depends on the number and size of "defects" plaguing the vesicle’s surface. In this paper we theoretically prove that a careful investigation of leak-age kinetics at early, intermediate, and late stages of the process can provide qualitative information on both the width and average spacing among the defects.