Hyperthermia therapy (HT) is becoming a well-recognized method for the treatment of cancer when combined with radiation or chemotherapy. There are many ways to heat a tumor and the optimum approach depends on the treatment site. This study investigates a composite ferromagnetic surgical implant inserted in a tumor bed for the delivery of local HT. Heating of the implant is achieved by inductively coupling energy from an external magnetic field of sub-megahertz frequency. Implants are formed by mechanically filling a resected tumor bed with self-polymerizing plastic mass mixed with small ferromagnetic thermoseeds. Model implants were manufactured and then heated in a 35 cm-diameter induction coil of our own design. Experimental results showed that implants were easily heated to temperatures that allow either traditional HT (39 °C-45 °C) or thermal ablation therapy (>50 °C) in an external magnetic field with a frequency of 90 kHz and amplitude not exceeding 4 kA/m. These results agreed well with a numerical solution of combined electromagnetic and heat transfer equations solved using the finite-element method.