Cytokinins are plant hormones that contribute to the regulation of a variety of developmental processes including apical dominance, flower and fruit development, leaf senescence, and seed germination. Numerous cytokinins have been characterized in different plant species. Differences among cytokinins are related predominantly to structural features, including the side chain that is attached to an adenine moiety, conjugation with sugars and phosphorylation. These hormones bind to cell surface receptors and initiate a signal transduction cascade that leads to activation of genes involved in tissue development. Over the past decade, many genes have been identified that affect cytokinin synthesis, transport, metabolism, and their function in growth regulation. In Arabidopsis, it appears that a gene family of over 20 members controls these processes. This paper presents an overview of recent experimental approaches and obtained results on the genes and corresponding proteins involved in cytokinin biosynthesis, modification, degradation and signal transduction.