We have investigated the efficacy of intraperitoneal or intrathoracic administration of hydroxyapatite particles (HAp) loaded carboplatin (CBDCA). HAp-CBDCA (HAp; 200 mg, CBDCA; 4 mg) was administered intraperitoneally to rats with peritoneal carcinomatosis. The area under the curve of the ascitic platinum (Pt) increased significantly with rats given HAp-CBDCA, and the omental Pt levels in the HAp-CBDCA group remained higher and longer. Additionally, the HAp-CBDCA group showed a trend toward longer survival when compared with the CBDCA alone group. In clinical use, HAp-CBDCA (HAp; 5 g, CBDCA; 150 mg) was administered intrathoracically to a patient who had undergone esophagectomy. The Pt in serum was detected until 7 days after administration of HAp-CBDCA.