Hybrid liposomes (HLs) composed of 90 mol% dimyristoylphosphatidylcholine (DMPC) and 10 mol% polyoxyethylene(23)dodecyl ether (C(12)(EO)(23)), having a hydrodynamic diameter under 100 nm, were preserved for a period of one month. The inhibitory effects of HLs on the growth of gastric carcinoma (CoRa 622 G6) cells in vitro were investigated. Decrease in mitochondrial membrane potential and activation of caspase-8, caspase-9 and caspase-3 were observed, indicating that apoptotic signals induced by HLs should pass through mitochondria and these caspases. Remarkable inhibitory effects on the metastasis of gastric carcinoma along with apoptosis and prolonged survival were obtained for mouse models of gastric carcinoma with peritoneal dissemination after the treatment with HLs in vivo.