To identify and characterize small GTP-binding proteins in plant cells, GTP-binding studies were performed with electroblotted plant proteins following SDS-polyacrylamide gel electrophoresis using [$alpha$-32P]GTP. Three speices of small GTP-binding protein (21, 23, and 27 kD) which have a specific GTP-binding property were identified in the membrane and cytosolic fractions of both monocotyledons (Zea mays) and dicotyledons (Glycine max). Moreover, these three species of small GTP-binding protein were gradually decreased when membranes were treated with hydroxylamine. This result indicates that these small GTP-binding proteins in plant cells are fatty acylated to the membrane lipids. The 27 kDa component was partially purified form hypocotyl membranes of Glycine max, following S-300 gel filtration, phenylsepharose CL-4B, hydroxyapatitie, and Q-sepharose column chromatography. This 27 kD protein was found to have both GTP-binding and GTPase activities.