Various plants containing pyrrolizidine alkaloids (PA) are visited by Lepidoptera, which congregate on dead stems, seeds, and foliage to feed. Most visitors to PA-plants belong to the nymphalid subfamilies Ithomiinae and Danainae and the moth families Ctenuchidae and Arctiidae. Ninety-six percent of ithomiines and danaines caught feeding at PA-plants are males which ingest alkaloids necessary for the production of PA-derived sex pheromones. Among Arctiidae and Ctenuchidae, however, many species show either unbiased or female-biased attraction patterns. Their visits may be linked to acquisition of PA's used for chemical defense or as yet unidentified nutritive substances. Extensive baiting with a variety of PA-plants as well as samples of etude alkaloids indicate that attraction is primarily the result of olfactory cues. Once a visitor lands on a PA-source, substances on the plant surface act as phagostimulants. Judging from attraction spectra of different PA-plant and chemical baits, at least 2 types of volatile attractants are involved: dissociated “esterifying acids” from the fused ring nucleus of the alkaloids, and substances derived from the nucleus itself. Preliminary observations of populations of Ithomiinae andDanausreveal that the presence of naturally occurring PA-sources are a major factor in determining population distribution, abundance, and reproductive behavior. The evolution of PA-attraction is discussed with respect to the various roles PA's may play in the Lepidoptera ingesting them.