An attempt has been made using Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy to see the molecular level interaction between indolicidin, a tridecapeptide known to possess antimicrobial activity, and model phospholipid bilayers. Initially, model lipid bilayers were assembled on ZnSe plates with compounds of dipalmitoylphosphatidic acid (DPPA), dipalmitoylphosphatidylcholine (DPPC), and dipalmitoylphosphatidylglycerol (DPPG) using the Langmuir-Blodgett (LB) method. From the FTIR-ATR dichroic ratios measured with and without rotation of the ATR plates, the LB lipid bilayers seemed to be described in terms of a uniaxial orientational model. Along with a cyclovoltammetry measurement, the ATR spectra dictated that indolicidin molecules were readily incorporated inside the acyl chains of the lipid bilayers. Furthermore, from the infrared absorption frequencies of amide I bands, indolicidin molecules that consisted of ill-defined random-coil structures in an aqueous medium appeared to adopt a 3(10)-helical conformation inside the lipid bilayers. This view was in good agreement with the electronic circular dichroism observed for PC (+10% cardiolipin) vesicles mixed with an indolicidin solution.