Plant fructokinases are the gateway to fructose metabolism. Here, we discuss the properties of published plant fructokinases and compare the available protein sequences. In addition, we speculate on the possible function of fructokinases as sugar sensors. A proposal is presented to clarify the confusing fructokinase nomenclature. Only a few plant fructokinase genes have been cloned but the recent isolations of two such genes in tomato and three in Arabidopsis have given this research an important impulse.