Abstract: A component mixing catheter (2) includes a catheter shaft (4) having proximal and distal ends (6, 8) and defining first and second lumens (10, 12). The catheter shaft has an exterior opening (16) at or near its distal end (8) which is fluidly coupled to the first lumen. One or more connecting passages (14) fluidly connect the first and second lumens at a position (30) spaced apart from the exterior opening. The second component passes through the connecting passage and mixes with the first component at a mixing region (25) within the first lumen just prior to exiting the catheter at the exterior opening for maximum therapeutic effect or diagnostic accuracy.