Parasitological Institute (formerly Helminthological Institute) was founded in 1953 as one of the initial SAS institutes in eastern Slovakia. A major task of the Institute in the beginning was to survey the helminth fauna in the geographic region of Slovakia and to investigate the biology, ecology and host-parasite relationships of helminths in man, animals and later also in plants. Important findings were obtained in the field of human helminthoses and helmintic zoonoses. A detailed research on trichinellosis yielded new facts on species composition, circulation in nature and treatment of this serious disease. Important findings on the biology of agents of trematodes in ruminants, on the pathogenesis of lungworms, helminths of fish and free-living animals served as the basis for practical measures to control helminthoses. The Institute greatly contributed to the understanding of the efficacy mechanism of new anthelmintic drugs. The phytohelminthological department has significantly contributed to the knowledge of plant parasitic nematode communities and their occurrence on agricultural crops and other plants. The current research employing modern cytogenetic and moleculo-biological methods has elucidated the revision of several helminth taxa. Anthelmintic resistance was ascertained in nematode species of small ruminants and horses in Slovakia. Attention of the Institute`s scientists is focused on important problems of ecological parasitology and on the negative effects of anthropically impaired environment on the parasite occurrence and the host behaviour. They follow also the interaction  between plant parasitic nematodes and viruses. New data have been gathered on the incidence and agents of important parasitic zoonoses such as larval toxocarosis, Lyme borreliosis and other zoonoses. Parasitological Institute SAS maintains a wide international cooperation with leading parasitological centres abroad. International helminthological symposia convened by the Institute are firmly included in the calendar of international parasitological meetings.