Abstract： AIM To investigate the changes of L-arginine(L-Arg)transportationkinetic characteristics in erythrocytes (RBC) and platelets (pt) of patients with essential hypertension (EH). METHODS 12 EH patients were studied with 16 normotensive people as control. The RBC and Pt were prepared and the transportation of L-Arg was measured by using the method described by Ghigo and Deliconstantins. RESULTS In EH patients, the ability of Pt L-Arg transportation was lower than control and Vmax decreased by 21% (P<0.01). In RBC, Saturable influx of L-Arg was mediated by teh classical cationic amino acid transport system Y+ and Y+L system with high affinity. Under zero-trans condition, the ability of L-Arg transportation in EH patients was lower than control. The Vmax for total L-Arg transport and via system Y+ decreased 36.8% and 42.5% respectively compared with control (P<0.01). But Vmax for L-Arg transport via system Y+L was not affected by EH. There was no obvious difference between the groups. CONCLUSION There might be disturbance of L-Arg transportation in human erythrocytes and platelets of patients with EH.