Self-assembled multilayer films (n congruent to 2-45) of the phospholipid dipalmitoyl L-alpha-phosphatidic acid (DPPA) have been shown, by polarized FTIR-ATR spectroscopy, to be well-ordered and packed in an all-trans configuration in a hexagonal crystalline lattice. Incorporation of the peptide gramicidin D results in a largely unperturbed lipid lattice (on the infrared length scale). This implies strongly that peptide aggregation occurs, as was also found for the same peptide in Langmuir-Blodgett multilayers of the same lipid.