We report in situ treatment, by focal hyperthermia, of a recurrent hepatoma in the transplanted liver of a 53-year-old man. Hyperthermia was generated by neodymium-yttrium-aluminum-garnet laser, which was delivered through a fiber placed inside a 19-gauge needle and inserted percutaneously into the liver under ultrasound guidance. The effect was monitored in real time by ultrasound and subsequently confirmed by computerized tomography and needle core biopsy. Objectively the tumor growth was halted for 3 months, indicating partial response to this minimally invasive treatment.