Анотация: A severe disease of cucumber, characterized by symptoms of root and stem rot, has been observed in 21 commercial greenhouses in Bulgaria. The pathogen was identified as F. oxysporum Schlechtend.: Fr. f.sp. radicis-cucumerinum D.J. Vakalounakis on basis of symptomsТ expression, experimental hosts range among plant species of cucurbit family and cultural and morphological characteristics of the obtained isolates. This is thought to be the first report of F. oxysporum f.sp. radicis-cucumerinum in Bulgaria