317 Brassinosteroids (BSs) are plant hormones of steroid nature, which have a wide spectrum of physiological effects. A characteristic property of BSs is a very strong stimulation of growth, which suggests that they have an active influence on the hormonal system of plants. Indeed, it was shown in various plant models and living plants that BSs change the content of various groups of plant hormones [1–3]. Earlier, we found that 24-epibrassinolide (EB) at the concentrations optimal for growth stimulation, 0.4 nM and 0.4 μ M, induces a sustained twofold increase in the free forms of cytokinins in the roots and sprouts of wheat seedlings but has no effect on content of indole-3-acetic (IAA) and abscisic (ABA) acids . These data indicate that EB may be involved in the regulation of metabolism of hormones of cytokinin nature. The fact that EB can rapidly change the content of various active forms of cytokinins (zeatin, zeatin riboside, isopentenyladenosine (IPA), and zeatin nucleotide) may serve as evidence for enhancement of cytokinin synthesis in the EB-treated seedlings , because it is known that IPA and zeatin nucleotide are the primary substances in the synthesis of cytokinins . On the other hand, an increased level of active forms of cytokinins in wheat seedlings during incubation with EB may be determined by inhibition of cytokinin oxidase (CKOX), a key enzyme involved in the cytokinin degradation . The effect of steroid hormones on CKOX activity in the plants has not yet been studied. For this reason, we studied the effect of EB on the activity and gene expression of cytokinin oxidase in wheat seedlings.