Objective: To investigate the association between KiSS-1 methylation and clinicopathological characteristics of gastric cancer and evaluate the role of peritoneal lavage fluid in detecting peritoneal metastases.Methods: The methylation status of KiSS-1 gene in 40 gastric cancer specimens, the corresponding adjacent normal mucosa, lymph nodes and peritoneal lavage fluid was investigated by methylation- spcific polymerase chain reaction(MS-PCR).Results: Aberrant methylation of KiSS-1 gene was detected in 55%(22/40) of the adjacent normal mucosa, 82.5% (33/40)of gastric cancer specimens, 80.95%(17/21) of the lymph nodes, and 42.5%(17/40) of peritoneal lavage fluid. Methylation in gastric carcinoma and lymphonode was more frequent than in non-neoplastic gastiric mucosa. Presence of KiSS-1 methylation in peritoneal lavage fluid was significantly correlated with tumor invasion (P=0.043). The accuracy of KiSS-1 methylation in peritoneal lavage fluid for diagnosing peritoneal metastasis was 70%, with a sensitivity of 77.8% and a specificity of 67.7%.Conclusion: Aberrant methylation of KiSS-1 gene is a common event in the occurrence and progression of gastric carcinoma, which may provide useful information for the early diagnosis of peritoneal metastases and a new therapy for gastric cancer.