Geographic isolation, altitude, climate, landscape and habitat are significant predictors of butterfly diversity in mountain ecosystems. Their diversity and its dependence on altitude, aspect (compass bearing) and biogeographic characteristics of the butterflies were surveyed on the karst mountain Biokovo in southern Croatia. The results affirm that there is a high diversity of butterflies in the study area and the species composition and biogeographic elements are more dependent on altitude than aspect of the mountain. The present study indicates that climate, relief and habitat preferences strongly influence the biogeographic features of species and the relationship between species richness per site and altitude, aspect and the altitude-aspect interaction. and Iva Mihoci, Vladimir Hršak, Mladen Kučinić, Vlatka Mičetić Stanković, Antun Delić, Nikola Tvrtković.