The interactions of butanol and mixtures of butanol and ethanol with dipalmitoylphosphatidyl choline (DPPC) liposomes have been investigated by both spectrophotometfic measurements and Fourier transform 13C nuclear magnetic resonance spectroscopy. The spectrophotometric experiments indicate that butanol exhibits the same effects on the thermotropic properties of DPPC as the other short chain alcohoB, methanol, ethanol and propanol, which have been shown to be. characteristic of the alcohol induced transition of the lipid to the interdigitated state. An additive effect of butanol and ethanol on the induction of the interdigitated phase in DPPC was also observed. A decrease in line width and increase in T 1 of the choline methyl signal were observed in the ~3C-NMR experiments conducted at 32Β°C when butanol was added to DPPC in increasing amounts suggesting an increase of disorder in the head group region of the lipid. Addition of ethanol to the NMR sample containing butanol produced hysteresis in the heating and cooling curves characteristic of the interdigitated state. In the interdigitated state, the choline methyl signal exhibited a T 1 value equal to that when the lipid is in the fluid state. The increase of mobility in the head group region in the intexdigitated gel state relative to the bilayer gel can be rationalized by the increase in surface area in that site when the lipid interdigitates.