Bacteria from the phyllosphere of an apple orchard in North Germany (“Altes Land”), transferred to non-chemical pest management ten years ago, were obtained in June and September 1995. One hundred and fifty epiphytic isolates were tested for inhibition of mycelial growth and conidial germination of Venturia inaequalis , the causal agent of apple scab. Twenty seven epiphytes displayed a distinct antagonistic activity in vitro . However, more than one third of these antagonists induced necrotic lesions on apple seedlings and hypersensitive reaction on tobacco. The other were ranked as to their efficacy. The antagonistic epiphytes were also taxonomically characterized by a polyphasic approach based on polyamine and fatty acid profiles and biochemical reactions. Eighteen Gram-negative strains belong to the genus Pseudomonas and two strains to the genus Erwinia . Six Gram-positive strains were allocated to the genus Bacillus and one to the genus Curtobacterium . Due to their strong inhibition of mycelial growth and conidial germination five strains of P. fluorescens and one strain of B. pumilus which display no plant-deleterious effects are suggested as potential biocontrol agents of V. inaequalis .