The premise that drugs should not be injected into the caudal body of reptiles because they will be carried by the renal portal system to the kidneys and rapidly excreted was tested by comparing the pharmacokinetics of carbenicillin in carpet pythons, Morelia spilota, injected anteriorly with those injected posteriorly. Seven carpet pythons were treated with 200 mg/kg carbenicillin administered intramuscularly. Three were injected anteriorly and four posteriorly. Serial blood samples were withdrawn over a period of 120 hr. Carbenicillin blood levels were measured over each time period and results used to calculate maximum carbenicillin plasma level, time of maximum plasma level, terminal half-life, area under the curve, volume of distribution and total body clearance. The study was repeated five months later with those snakes that were previously injected anteriorly now being injected posteriorly and vice versa. Blood was taken and the same parameters calculated. Following all calculations no significant differences in pharmacologic parameters were found based on injection site. Dissection of three dead carpet pythons determined that renal portal anatomy was the same as that described for other python species. Radio-opaque dye was injected in the caudal vein of one python and observed radiographically to pass via the afferent renal portal veins through the kidneys and enter the efferent renal portal veins.