Cytokinin activity was determined in embryo and endosperm tissues from 30-day (stage 1), 55-Jay (stage 2), and 80-day (stage 3) old fruits of Cassia fistual. High cytokinin activity was associated with stage 1 and the least in stage 3. This indicated that the cytokinins disappeared during the course of seed development. Sephadex LH-20 column chromatography with 35% ethanol indicated the presence of cytokinins coeluting with zeatin glucoside, zeatin riboside, and zeatin. Qualitatively the cytokinins in the embryo and endosperm were identical at all the stages. The putative zeatin glucoside predominated at stage 1 but was absent in the later stages while only zeatin riboside was present at stage 3. The high cytokinin activity in the endosperm at early stages indicates that it may act as a supplier of cytokinins to the embryo during these periods. The possible significance of these findings is discussed. © 1984, Gustav Fischer Verlag, Stuttgart. All rights reserved.