An infusion catheter assembly has the ability to infinitely titrate the length of a porous fluid distribution section in situ. The infusion catheter assembly thereby provides a length of infusion that can be infinitely varied over a prescribed range, to control the effective infusion length and the rate of infusion. Using the infusion catheter assembly, a physician has the capability to treat only the length of the vessel desired, thereby preventing excessive drug/patient exposures. The porous fluid distribution section can include an array of spaced apart apertures that vary in size and/or density along the length of the porous fluid distribution section, such that the flow rate remains essentially constant for a given inlet pressure independent of the effective infusion length.
