Several oligopeptides, derived from certain proteins, translocate as a form fused to small molecules or exogenous proteins across the plasma membrane into cells. Some of these oligopeptides, the so-called protein-transduction domains (PTDs), contain a high proportion of basic residues. The translocation of some of these basic PTDs, such as oligoarginines, has been studied as chemically fused forms to other organic compounds. In this study, we also tested to determine whether or not oligoarginines, when fused genetically to an exogenous protein such as GFP, are also able to translocate efficiently across the plasma membrane. The oligoarginine Rn (n = 5,6,7,8,9)-GFP fusion proteins were translocated quite efficiently, and the transduction efficiency increased in proportion to the number of arginine residues. However, the cellular uptake of the oligolysine-GFP fusion proteins was less efficient than that of the corresponding oligoarginine-GFP fusion proteins. When fused to GFP, the translocation efficiency of R5 was similar to that of Tat(49-57)(RKKRRQRRR). This finding suggests that the arginine homo-oligopeptide is more efficient than other PTDs which contain a mixture of basic residues. On the other hand, both the K9- and Tat(49-57)-GFP fusion proteins were transduced with similar efficiencies. It appears that basic oligopeptides may be useful for the efficient translocation of diverse exogenous proteins as genetically fused forms.