The advent of ultra-fast imaging techniques has extended the utility of magnetic resonance imaging (MRI) from a static and purely diagnostic status to an imaging modality ideally suited for a number of therapeutic applications. These advances--along with the recent development and refinement of miniature intravascular imaging catheters and MRI-compatible guidewires, balloon catheters, and radiofrequency ablation catheters--have created an exciting forum of novel approaches for detecting and treating both acquired and congenital cardiovascular disease. This review covers the current state of the art in fast cardiovascular MRI, catheter-tracking techniques for MR fluoroscopy, and currently available interventional MRI systems. Early diagnostic and therapeutic applications, such as high-resolution intravascular and intracardiac imaging, balloon angioplasty, stent placement, and radiofrequency ablation techniques, are discussed and extended to several potential approaches specific to pediatric cardiac therapeutic catheterization. Lastly, safety aspects of MR-guided interventional procedures are presented.