Isolating the enzymes responsible for fructan synthesis in plants has been hampered by unsuitable assays used during purification. It is believed that there are two enzymes necessary for fructan synthesis in higher plants, one initiating synthesis utilizing sucrose as donor and the other elaborating the polymer using fructan oligomers as donor. In this paper, a rapid quantitative assay is described to measure the latter fructosyl transfer. The activity was absent from leaves that were not synthesizing fructan. Activity in crude extracts showed a hyperbolic dependence upon sucrose concentration. Activity against 1-kestose showed a pronounced optimum, suggesting that self-transfer also occurred.