Background and purpose: ~(125)I seeds implantation was mainly used in the treatment of prostate cancer. Recently, this technique has been used to treat other solid tumors such as lung cancer or liver cancer. The objective of this study was to evaluate the technique and effect of interstitial brachytherapy for intraperitoneal tumors. Methods: From February 2006 to January 2009, 20 patients with intraperitoneal tumors were treated with interstitial brachytherapy. The study included 7 cases with liver metastases, 8 cases with retroperitoneal lymph nodes metastases, three cases with pancreatic cancer, 2 cases with pelvic recurrence of rectal cancer. Results: All the patients received CT scan follow up 2 months after treatment. CR, PR, SD, PD were obtained in 7, 7, 3 and 3 cases, respectively. The total response rate was 70%. Conclusion: Interstitial brachtherapy is one of the effective treatments for the patients with intraperitoneal tumor. The adverse events are tolerable but the long-term benefits of this treatment method need further study.