Early-stage lung cancer detection is the first step towards successful clinical therapy and increased patient survival. Clinicians monitor cancer progression by profiling tumor cell proteins in the blood plasma of afflicted patients. Blood plasma, however, is a difficult cancer protein assessment media, because it is rich in albumins and heterogeneous protein species. We report herein a method to detect the proteins released into the circulatory system by tumor cells. Initially, we analyzed the protein components in the conditional medium (CM) of lung cancer primary cell or organ cultures, and in the adjacent normal bronchus using 1-D PAGE and nano-ESI-MS/MS. We identified 299 proteins involved in key cellular process such as cell growth, organogenesis and signal transduction. We selected 13 interesting proteins from this list, and analyzed them in 628 blood plasma samples using ELISA. We detected 11 of these 13 proteins in the plasma of lung cancer patients and non-patient controls. Our results showed that plasma MMP1 levels were elevated significantly in late-stage lung cancer patients, and that the plasma levels of 14-3-3 sigma, beta and eta in the lung cancer patients were significantly lower than those in the control subjects. To our knowledge, this is the first time that fascin, ezrin, CD98, annexin A4, 14-3-3 sigma, 14-3-3 beta and 14-3-3 eta proteins have been detected in human plasma by ELISA. The preliminary results showed that a combination of CD98, fascin, PIGR/SC and 14-3-3 eta had a higher sensitivity and specificity than any single marker. In conclusion, we report a method to detect proteins released into blood by lung cancer. This pilot approach may lead to the identification of novel protein markers in blood and provide a new method of identifying tumor biomarker profiles for guiding both early detection and therapy of human cancer.