Fourier transform infrared spectroscopy has been used to examine the structural dynamics of lipid fatty acyl chains, lipid/water interface and phosphate headgroup of phospholipid mixtures containing dioleoylphosphatidylethanolamine (DOPE) and dioleoylphosphatidylcholine (DOPC) in lamellar liquid crystalline (Lα) and inverted hexagonal (HII) phases. The CH2 symmetric stretching, CO stretching and OPO symmetric and antisymmetric stretching bands of the lipids were measured at different lipid compositions (0–100% DOPE) and temperatures (0–75°C). For pure DOPE, a significant increase in the CO and a slight increase in the CH2 stretching frequencies were found at 5–10°C which corresponds to the known Lα-HII transition temperature of DOPE. No significant changes were observed for the OPO symmetric and antisymmetric frequencies. Upon increasing the content of DOPC in the DOPE/DOPC binary mixtures, the Lα-HII transition became broadened and shifted to higher temperatures. This behavior was further quantitated by the use of a contour plot of CO frequency as a function of temperature and PE%. Ternary mixtures of DOPE/DOPC/tetradecane were also studied at a fixed DOPE/DOPC ratio (75:25) and at 23°C. The CO stretching frequency increased as the oil concentration varied from 0% to 6% (oil/lipid weight%) and remain constant as the oil content increased from 6–20%. A slight decline in the CH2 frequency was also noticed at 6–8% tetradecane. These results agreed with the known HII promotion effect of tetradecane in the binary DOPE/DOPC mixtures.