Thirty two bacteria antagonistic to a number of phytopathogenic fungi were isolated from soil samples. One bacterial strain, designated as M 51, appeared to be particularly active towardsF. oxysporum f. sp.dianthii, in vitro andin vivo and it was inhibitoryin vitro to three otherFusarium spp. used. Tests to find if there was protection against fusarium wilt were carried out by three different methods of inoculation of the cuttings: a) dipping of cuttings for ten minutes in bacterial suspension; b) spraying of suspension on perlite where the rooted cuttings were planted; c) spraying the greenhouse bench rooting boxes, where the non-rooted cuttings were planted, with bacterial suspension. Following this all the cuttings were transplanted into soil naturally highly infested withFusarium oxysporum f. sp.dianthii (3000 units/g). Good protection against fusarium wilt was obtained for cuttings inoculated by method (b). However protection decreased gradually about 60 days after they were transplanted; both control and inoculated cuttings showed a comparable mortality rate. Method of inoculation and the development of the protective effect are discussed.