Updated FTP location. Glioblastoma (GBM) is the most common and aggressive brain tumor in adults. The purpose of the present study was to identify GBM cell-selective secreted proteins by analyzing conditioned media (CM) from GBM, breast, and colon cancer cell lines using sequential window acquisition of all theoretical spectra mass spectrometry (SWATH-MS) and targeted proteomics. We identified 26,041 peptides derived from 2,371 proteins in the CM from GBM and the other cancer cell lines. Among the proteins identified, 15 showed significantly higher expression in the CM from GBM cell lines than in those from other cancer cell lines.