Mathematic manipulation was performed on the pharmacokinetic equation parameters of CPK after intravenous administration of 300, 500 and 860 U/kg body weight dose in sixteen male rabbits to investigate the effect of disposition model with or without the involvement of inactivation in the Iymphatic system on the micro-rate constants of CPK. The pharmacokinetic equations and the estimation of micro-rate constants were derived for two distinct two-compartment body models. The mean hybrid distribution rate constant (α) and elimination rate constant (β) were 0.630 +- 0.176 h-1(mean +- S.D., n = 16) and 0.106 +- 0.016 h-1, and were independent on the dose size.The mean micro-rate constants for the model involving an apparent first-order inactivation process of CPK in the Iymph were estimated to be 0.092 +- 0.038 h-1 (k10), 0.245 +- 0.061 (k12) and 0.321 +- 0.146 h-1 (k2l). Student t-test showed the difference of the micro-rate constants among the different dose size and between the two models was insignificant due to the relatively large intersubject variability in rabbits. However,the result of kinetic analysis implied the possible involvement of reticuloendothelial system in the elimination of CPK in vivo.