The kanamycin sensitivity of callus growth and adventitious shoot and root formation was studied in several cultivars of Vitis vinifera L. and in V. rupestris Scheele cv. St. George to investigate the suitability of kanamycin resistance as a selectable marker for grape transformation. Kanamycin concentrations ranged from 0 to 30 mg/l. Carbenicillin was added to the medium in all experiments at concentrations of 500 or 250 mg/l, as normally used in cocultivation experiments with Agrobacterium. Callus formation, root initiation, and adventitious shoot formation were completely inhibited by 20, 10, and 7 mg/l kanamycin, respectively; suggesting that these are the minimum concentrations that should be necessary to select transformed plants. Carbenicillin produced inhibitory effects that sometimes resembled those of growth regulators. The high kanamycin sensitivity of adventitious shoot formation in grape exceeds that reported for any other plant species and is likely to hinder the recovery of transformed plants.