Most butterflies of the tribe Troidini (Lepidoptera: Papilionidae) sequester aristolochic acids (AA) for their protection. These acids are derived from their host plants -family Aristolochiaceae- upon which they feed on during their larval stages. Using analytical High Performance Liquid Chromatography (HPLC) methods we were able to detect the presence of aristolochic acids I and II both in the young leaves of Aristolochia maxima (Aristolochiaceae) and in the caterpillars of the butterflies Battus polydamas polydamas and Parides panares erythrus (Papilionidae, Papilioninae). Aristolochic acid I was the major constituent found, followed by lesser amounts of Aristoloquic acid II. These results confirm that the host-animal interaction among butterflies of the studied species and A. maxima plants is mediated, by aristolochic acids.