A caged, photocleavable derivative of dioleoylphosphatidylethanolamine (DOPE) called NVOC-DOPE was prepared by reaction of DOPE with 6-nitroveratryloxycarbonyl chloride. In contrast to egg phosphatidylethanolamine (EPE), NVOC-DOPE or its 1:1 mixture with EPE forms liposomes at both pH 7.4 and 5.0. Photolysis (lambda > 300 nm) of aqueous liposomal dispersions of NVOC-DOPE at pH 9.0, 7.4, or 5.0 results in complete conversion to DOPE and subsequent release of entrapped calcein dye. The temporal and spatial control associated with the photorelease technique suggests that NVOC-DOPE can be used to study a range of important dynamic membrane processes such as membrane fusion and the action of membrane-associated enzymes.