A dual access infusion or monitoring system comprises implantable apparatus and an injection needle. This system enables one to introduce into or withdraw from the apparatus, after it is implanted, a plurality of fluids simultaneously with only a single penetration of the patient's skin. The implantable apparatus includes a sealed housing with an inlet passage extending into the housing which passage has an outer end adjacent to the housing surface and an inner end located inside the housing. A needle stop is positioned at the inner end of that passage and self-sealing septa are mounted at different locations along the passage at selected spacings from the needle stop so as to divide the passage into aligned compartments or segments each of which has its own fluid outlet. The injection needle includes a plurality of lumens, the number of same corresponding to the number of different compartments in the apparatus housing. The proximal ends of the lumens are connected to different passages in a hub and the lumens have outlet openings spaced at different locations along the needle from the needle tip in correspondence with the spacings of the housing passage compartments so that when the needle is inserted into the housing passage through the septa until the needle bottoms on the needle stop, each outlet opening in the needle will be positioned in a different compartment in the housing passage, with all of the needle openings being isolated in a fluid-tight manner from one another and from the atmosphere by at least one septum.