Amoebic keratitis is difficult to treat without total efficacy in some patients because of cysts, which is less susceptible than trophozoites to the usual treatments. The aim of this study is to evaluate the in vitro amoebicidal activity of the methanolic extracts of Peucedanum caucasicum, Peucedanum palimbioides, Peucedanum chryseum, and Peucedanum longibracteolatum, which are endemic in Turkish flora except P. caucasicum. Extracts were evaluated for their amoebicidal activities using an inverted light microscope. In the presence of methanolic extracts (ranging from 1.0 to 32.0 mg/ml), numbers of the viable Acanthamoeba castellani trophozoites and cysts were determined during the experimental process (72nd hour). All of the extracts showed a time and dose-dependent amoebicidal action on the trophozoites and cysts. Among the extracts tested, P. longibracteolatum showed the strongest amoebicidal effect on the trophozoites and cysts. In the case of 32 mg/ml concentration of extract, no viable trophozoites or cysts were determined between 24th and 72nd hour. Similar results were obtained from the extract at 16.0 mg/ml concentration against trophozoites. At this concentration value, number of viable cysts was determined as 10.6 +/- 2.1 in the 24th hour. trophozoites were determined in the 48th hour. At the same concentration, 51% of the cysts were killed by the extract in the 72nd hour. As expected, cysts were found more resistant to the extracts than the trophozoites.