The drug delivery (DD) process of benzene derivatives, n-propylbenzene (PrBe) and benzyl alcohol (BzOH), delivery DD process of benzene derivatives n-propylbenzene (PrBe) and benzyl alcohol (BzOH) from water to phospholipid vesicles is first monitored by noninvasive NMR technique. The bilayer interface and interior as delivery sites are unambiguously specified by taking advantage of the site selectivity of NMR. Chemical shift differences of the ring proton signals provide direct evidence for the penetration of the "drugs" into the bilayer within a few minutes. PrBe is deeply penetrated into the hydrophobic chain region of the bilayer core. In contrast, BzOH is preferentially trapped in the interfacial region near the carbonyl group of the phospholipid, with the methylene group oriented toward the inside of the bilayer. The delivery site of BzOH is characterized by the doublet of the ring proton NMR signal, which is ascribed to BzOH delivered into the outer and inner layers of the vesicle. This is also confirmed by C-13 NMR, for the first time applied to specify the delivery site. UV absorption spectra of PrBe and BzOH in vesicles are consistent with the delivery sites determined by NMR. Application of the molecular level study of the DD processes to recent severe problems of endocrine disruptors (EDs) is finally proposed as a basis for the comprehensive understanding of the molecular mechanism of the membrane disrupting action and for the purpose of detoxication and the prevention of ED accumulation.