Laserthermia by a novel interstitial probe adapted to low power Nd-YAG laser machine was used to treat small hepatocellular carcinoma (HCC). The set condition was 43-45 degrees C in thermocouple with power of 2-3 W and the duration 20-30 min. In the 5 cases studied, 1 had a good result with total necrosis of the tumour without recurrence in 16 months. 1 died of liver failure 2.5 months later although death was not related to the procedure. 1 patient died of progressive disease 18 months later. The remaining 2 had recurrent tumours 5 and 12 months later, although the treated small tumours showed good response. Histological examination showed cell degeneration and necrosis. It is concluded that laserthermia is potentially useful in the treatment of the patients with small HCC.