Camptothecin (CPT) is a strong antitumor agent, but its use limited by its low solubility and the instability of the active lactone form. To overcome these difficulties, liposomes incorporating CPT (CPT liposomes) were designed and tested. CPT liposomes were formulated by the addition of 3,5-bis(dodecyloxy)benzoic acid (DB) to polyethylene glycol-containing liposomes, and by coating the surface of the liposomes with human serum albumin (HSA, HSA-DB-L). HSA-DB-L successfully entrapped CPT with about 80% efficiency and with a particle size of about 150 nm. HSA-DB-L showed attenuated drug release and storage stability. Pharmacokinetics studies in mice showed that i.v. injection of HSA-DB-L (2.5 mg/kg) led to prolonged circulation in the plasma; the area under the curve was 22-fold higher than that of CPT solution. The tumor growth in mice with subcutaneous transplantation of colon 26 tumor cells was significantly inhibited after a single i.v. injection of HSA-DB-L at a dose of 15 mg/kg without any significant body weight loss. HSA-DB-L increased the accumulation of CPT in tumor tissue significantly (9.6-fold) more efficiently than CPT solution 24 h after i.v. injection. These findings suggest that HSA-DB-L could increase the stability and the antitumor effect of CPT. CPT delivery by novel liposome formulations is a potential approach for effective treatment of cancer.