Abies nordmannianaandPicea abiesseedlings were inoculated with a wild‐type (C 58) or an attenuated strain (rooter or shooter mutants) ofAgrobacterium tumefaciens. Large tumours were formed onA. nordmannianain response to the wild‐type and rooter strains, 60–65%of the seedlings being susceptible. Smaller tumours were formed onPicea abiesin response to the wild‐type strain, at least 12% of the seedlings being susceptible. Tumours from both species induced by the wild‐type strain grew in vitro on medium without added phytohormones.