Accumulation of ascites fluid often observed in some solid tumors is one of the most devastating conditions of a patient's difficulty in responding to treatment. and to a decrease in the quality of life. Various factors are thought to be associated with the formation of cancer-induced fluid accumulation and hyperpermeability of a blood vessel is thought to go with this process. Here, we report a new factor that is involved in this process, e.g., autocrine motility factor (AMF). AMF is a tumor-related cytokine which stimulates the tumor cell locomotion and migration and promotes tumor cell invasion during metastasis. AMF secretion and its receptor (AMFR) expression in tumor cells are closely correlated with disease aggravation of convalescence. The response of endothelial or mesothelial cellular morphological alternation to AMF leads to motile enhancement and vascular permeability. Tumor AMF induces gaps in an endothelial or mesothelial monolayer by stimulating a cellular movement, and accelerates the ascites accumulation. And treatment experiment with anti-AMF antibody succeeded in the reduction of the ascites accumulation. which renders AMF to the target molecule. It is suggested that AMF is one of the significant factors which relates to various pathological malignancies induced by tumor mass. and understanding of its function could benefit prognosis and treatment. (C) 2002 Elsevier Science (USA). All rights reserved.