Intraperitoneal adminstration of radioisotopes is suggested to treat the metastatic ovarian cancer in the pertioneal cavity. Administering beta-emitting radioisotopes into the pertioneal cavity allows the maximum energy delivery to the cancerous cells of the pertioneal wall surface while sparing the normal cells located in deep site of the peritoneal wall. In this study, dose estimates of the peritoneal wall are provided to be used for prescribing the amount of 166Ho-chitosan complex administered. The 166Ho-chitosan complex diffused in the peritoneal fluid may attach to the peritoneal wall surface. The attachment fraction of 166Ho-chitosan complex to the peritoneal wall surface is obtained by simulating the ascites with Fischer rats. Both volume source in the peritoneal fluid and the surface source over the peritoneal wall surface are counted for the contribution to the peritoneal wall dose. The Monte Carlo code EGS4 is used to simulate the energy transfer of the beta particles emitted from 166Ho. A plane geometrical model of semi-infinite volume describes the peritoneal cavity and peritoneal wall. A semi-infinite plane of 10 μm in thickness at every 1 mm of depth in the peritoneal wall is taken as the target in dose estimation. Greater han 98 percents of attachment fraction has been observed from the experiments with Fischer rats. Given 1.3μCi/㎠ and 2.4μCi/ml of uniform activity density, absorbed dose is 123 Gy, 8.59 Gy, 3.00 Gy, 1.03 Gy, and 327 Gy at 0 mm, 1 mm, 2 mm, 3 mm, and 4 mm in depth to the peritoneal wall, respectively.