`McIntosh' apple shoots were inoculated in vitro with Agrobacteriumtumefaciens strain tms328::Tn5 (tms) carrying a functional cytokinin gene. Callus tissue, removed from the infected stems, produced shoots on shoot proliferation medium. After three subcultures, axillary shoot production from a tms-infected putative transformant was eight times that of controls. Subsequent shoot production on three different levels of BA (3, 6 and 10 uM) was significantly greater than from controls on all levels of BA. PCR analysis of putative transformants revealed an expected 503 bp DNA fragment corresponding to the amplified portion of the cytokinin gene. After 6 months of in vitro propagation, proliferation rates of shoots obtained from the original transformants were similar to the controls and the expected PCR fragment of 503 bp could only be detected by Southern analysis. Even though the T-DNA appears to be lost from the apple genome, the data suggest that the tms strain may be useful in co-infection experiments to induce shoot formation, thus avoiding difficult regeneration procedures.