Differential scanning calorimetry can be used to effectively study the thermotropic phase behavior of phospholipid bilayers. In the current study, this technique was applied to analyze the effects of varying concentrations of n -butanol, sec -butanol, and tert -butanol on the phase transitions of dipalmitoylphosphatidylcholine (DPPC), a 16-carbon acyl chain phospholipid. The threshold concentration for the induction of the interdigitated phase was identified by the disappearance of the pretransition and the onset of a large hysteresis between the heating and cooling scans of the gel-to-liquid main transition temperature. This critical concentration increased with greater branching of the butanol isomers. At low concentrations, a downward shift in the main transition temperature was observed with all of the isomers. Following the point of interdigitation however, the behavior of DPPC in the presence of each isomer varied. In the case of n -butanol and sec -butanol, there was a slight increase in the main transition temperature after the critical concentration but then a gradual downward trend resumed. A clear biphasic effect was observed for DPPC in the presence of tert -butanol.