Background Peritoneal dissemination of hepatocellular carcinoma after tumour rupture is common, and the current treatment for this situation is metastectomy. However, the therapeutic outcome is often unsatisfactory. Photodynamic therapy combines a non-toxic photosensitiser, oxygen, and visible light to produce a cytotoxic effect. Photodynamic therapy using photofrin, a haematoporphyrin derivative, and laser light of 630nm wavelength is a potential treatment for peritoneal cancer dissemination, because its cytotoxicity is limited to superficial lesions. Methods GP7TB cells, a rat HCC cell line, were intraperitoneally injected into male F344 rat. After 14days, 18 tumour-bearing animals were divided into three groups and photofrin was administered intraperitoneally to the animals (group 1) at the dose of 20mg/kg at 24h before tumour illumination, and administered intravenously via the caudal vein at 5mg/kg in group 2 animals. For intraperitoneal photodynamic therapy, the peritoneum was filled with normal saline, and illuminated with a fibre optic cable. Tumour sites were irradiated with a 630-nm CW diode laser with a dose of 100J/cm2. 4days after treatment, a total count of tumour nodules was done, as was an assessment of tumour changes after treatment. Findings Photodynamic therapy in group A and B resulted in a significant lower count of tumour nodes compared with the control group. Percentage of tumour necrosis in group 1 was significantly higher than in group 2 and control group (92% versus 42.5% in group 2 and 12.0% in the control group). Significant increases in TUNEL-positive cells and Ki-67-positive cells were seen after photodynamic therapy in treated groups. Interpretation These preliminary results demonstrate the feasibility of photodynamic therapy for treatment of peritoneal dissemination of hepatocellular carcinoma.