Giant vesicles (GVs) of functionalized, double-chain surfactant 1 (2-hydrazino-N-methyl-N,N-didodecyl2-oxoethanaminium bromide) were observed by phase-contrast optical microscopy as they underwent chemical reactions with 2 (O-methyl S-benzyl phenylphosphonothioate) in a pH 9.0 borate buffer at 23 degreesC. The GVs were damaged and ultimately converted into oil-like droplets. Also, GVs of 1 containing fluorescent dye 7 (1-methyl-7-hydroxyquinolinium iodide) were observed by simultaneous optical and epifluorescence microscopy as they underwent reactions with 2. The reactions effected the loss of 7 from the GVs.