A matched-dipole type catheter antenna is described for intracavitary and/or transluminal microwave treatment of diseases that may be responsive to thermal ablation therapy. This cap-choke antenna consists of an annular cap and coaxial choke design that can yield specific absorption rate (SAR) distributions in, and can produce heating of, tissue surrounding the distal end of the catheter antenna. The cap-choke antenna is simple in construction, provides the desired SAR distribution, and is efficient, i.e., the measured power reflection coefficient is 2% in tissue equivalent phantom modeling materials.