24Lung cancer is one of the ten most common causes of death worldwide, so that the search for 25 early diagnosis biomarkers is a very challenging task. Bronchoalveolar lavage fluid (BALF) provides 26 information on cellular and biochemical epithelial surface of the lower respiratory tract constituents and 27 no previous metabolomic studies have been performed with BALF samples from patients with lung 28 cancer. Therefore, this fluid has been explored looking for new contributions in lung cancer metabolism. 29In this way, two complementary metabolomics techniques based on direct infusion high resolution mass 30 spectrometry (DI-ESI-QTOF-MS) and gas chromatography mass spectrometry (GC-MS) have been 31 applied to compare statistically differences between lung cancer (LC) and control (C) BALF samples, 32 using partial least square discriminant analysis (PLS-DA) in order to find and identify potential 33 biomarkers of the disease. A total of 42 altered metabolites were found in BALF from LC. The metabolic 34 pathway analysis showed that glutamate and glutamine metabolism pathway was mainly altered by this 35 disease. In addition, we assessed the biomarker specificity and sensitivity according to the area under the 36 receiver operator characteristic (ROC) curves, indicating that glycerol and phosphoric acid were potential 37 sensitive and specific biomarkers for lung cancer diagnosis and prognosis.