Kaniv Nature Reserve was established in 1923 to preserve its unique nature, and its historical and archaeological relics and monuments. From 1939 the reserve (area 20.27 square km) has been used as a field station for students of the Natural Sciences faculties of the Kiev Taras Shevchenko University. Though the reserve is used for many diverse activities, the top priorities are to conserve its natural condition. protect its biodiversity and to monitor the ecosystem. Due to its location, relief and strong history of conservation, great biodiversity has been preserved in this area over the last 75 years. Based on recent recording 1100 species of vascular plants (22 included in Red Data Book), 1120 species of fungi (6 from Red Data Book) and about 300 species of mosses and lichens are known in the reserve. There are 333 vertebrate species including 31 from the Red Data Book. Among 9125 species of invertebrates known in the reserve, 32 are rare. It is worth noting that in general biodiversity and in the number of rare species by area unit, Kaniv is one of the leading nature reserves, not only in Ukraine but in the whole of the former Soviet Union. One reason for this is that the plants and animals of the area have been intensively explored. The results of many years' monitoring and repeated recording of plants and animals indicate that the reserve's biota is in a satisfactory condition. Some species seem to vary in abundance, and this can be explained by human pressure and natural successions in the reserve's ecosystems. The results of many years' study show that the two generally accepted functions of the reserve, preservation of its natural condition and biodiversity conservation, can at times be incompatible. New scientific approaches to the study of nature reserves and further theoretical research in this field are required.