Abstract: Polyamidoamine (PAMAM) G5.0 dendrimers were synthesized and characterized.The complex of PAMAM with fluorouracil (5-Fu) was prepared by equilibrium dialysis,and the binding capacity of PAMAM to 5-Fu was studied.The pharmacokinetics in rats receiving oral dosing of 5-Fu suspension and complex were investigated by HPLC. The maximum combination of complex occurred when molar ratio of 5-Fu and PAMAM G5.0 was about 250. The average size of complex was (30.2±4.9)nm.Oral pharmacokinetics in rats showed that the K_a,c_max of the complex had a significant increase (P<0.01),and AUC_0-∞ was 1.37 times to that of the suspension group.These results indicated that PAMAM can increase the absorption of 5-Fu significantly and improve its oral bioavailability.