Purpose: Metastatic prostate cancer is a major cause of death of men in the United States. Expression of met, a receptor tyrosine kinase, has been associatedwithprogressionof prostate cancer. Experimental Design: To investigate met as a biomarker of disease progression, urinary met was evaluated via ELISA inmen with localized (n = 75) and metastatic (n = 81) prostate cancer. Boxplot analysis was used to compare the distribution of met values between each group.We estimated a receiver operating characteristic curve and the associated area under the curve to summarize the diagnostic accuracy of met for distinguishing between localized and metastatic disease. Protein-protein interaction networking via yeast two-hybrid technology supplemented by Ingenuity Pathway Analysis and Human Interactome was used to elucidate proteins and pathways related to met that may contribute to progression of disease. Results: Met distributionwas significantly different between the metastatic group and the group with localized prostate cancer and people with no evidence of cancer (P < 0.0001).The area under the curve for localized and metastatic disease was 0.90, with a 95% confidence interval of 0.84 to 0.95.Yeast two-hybrid technology, Ingenuity PathwayAnalysis, and Human Interactome identified 89 proteins that interact with met, of which 40 have previously been associated with metastatic prostate cancer. Conclusion: Urinary met may provide a noninvasive biomarker indicative of metastatic prostate cancerandmay be a central regulator ofmultiple pathways involved in prostate cancer progression.