Cytokinin is one of major growth regulators in plants. In this study, the gene isopentenyl transferase (jpt) which encodes a key enzyme involved in the biosynthesis of the growth regulator cytokinin isolated from Agrobacterium tumefaciens was introduced ito tobacco plant via Agrobacterium-mediated transformation. The jpt gene was modulated using the proteinase inhibitor II (PI-IIK) promotor. In general, this promoterlipt gene fusion resulted in overproduction of cytokinins throughout the transgenic plants. The overproduction of cytokinin caused dramatic changes in morphology of the plant, including stem thickness and reduced root development. The studies reported in this paper were initiated to examine the consequences of overproduction of cytokinin in plant.