Induction heating of small, cylindrical ferromagnetic implants (1.4 cm long and 1 mm in diameter) is a method for treating deep-seated tumors. These implants, or ThermoRods trade mark, are placed within a lesion in 1-cm(2) arrays and are exposed to an alternating magnetic field. The implants absorb energy from that field and transfer it as heat to the surrounding tissue. Each ThermoRod trade mark offers approximately 400 mW of power, and to kill cells, the target temperature must be greater than 42 degrees C. In this work, a magnetic field-focusing device is employed to concentrate the induced magnetic flux toward a local region near the base of the prostate to increase the power output of proximal ThermoRods trade mark. This, in turn, allows for more complete thermal ablation of lesions near the base of the prostate where the heat-sink characteristics of the bladder can cause significant power losses. Boundary element analysis and in vitro testing have shown that the use of a ferrofluid-based field-focusing device can lead to a significant increase in power output of approximately 25% and 13%, respectively, of proximal ThermoRods trade mark. These preliminary results indicate that the incorporation of such a ferrofluid-based focusing device into ThermoRod trade mark treatments is promising for the avoidance of significant power loss and for assuring complete thermal ablation of prostatic lesions.