Differential scanning calorimetry (DSC) was employed to study the effects of n-propanol and isopropanol on the phase transitions of dipalmitoylphosphatidylcholine (DPPC), a 16-carbon acyl chain phospholipid. Various concentrations of both alcohols were used in this investigation.The biphasic effect, observed above 0.39M for n-propanol and 0.52M for isopropanol, was identified by the large hysteresis between the heating and cooling scans on the gel-to-liquid crystalline main transition temperatures. At low alcohol concentrations, the main transition temperatures decreased with increasing alcohol concentrations. However, after the critical concentration, the main transition temperatures started to increase due the formation of the more stable interdigitated gel phase. The induction of this particular gel phase is identified not only by the biphasic effect, but also the disappearance of the pretransitions and the presence of an extra peak on the cooling scans.