In the course and prognosis of colorectal cancer (CRC), early detection and treatment are essential factors. Fecal immunochemical tests (FITs) are currently the most commonly used non-invasive screening tests for CRC and premalignant (advanced) adenomas, however, with restricted sensitivity. We hypothesized that fecal volatile organic compounds (VOCs) may serve as a diagnostic biomarker of CRC and adenomas. In this proof of concept study, we aimed to assess disease-specific VOC smellprints in fecal gas to distinguish patients with CRC and advanced adenomas from healthy controls. Fecal samples of patients who were scheduled to undergo an elective colonoscopy were collected. An electronic nose (Cyranose 320V R ) was used to measure VOC patterns in fecal gas from patients with histopathologically proven CRC, with advanced adenomas and from controls (no abnormalities seen at colonoscopy). Receiver operator characteristic curves and corresponding sensitivity and specificity for detection of CRC and advanced adenomas were calculated. A total of 157 stool samples (40 patients with CRC, 60 patients with advanced adenomas, and 57 healthy controls) were analyzed by electronic nose. Fecal VOC profiles of patients with CRC differed significantly from controls (area under curve 6 95%CI, p-value, sensitivity, specificity; 0.92 6 0.03, <0.001, 85%, 87%). Also VOC profiles of patients with advanced adenomas could be discriminated from controls (0.79 6 0.04, <0.001, 62%, 86%). The results of this proof of concept study suggest that fecal gas analysis by an electronic nose seems to hold promise as a novel screening tool for the (early) detection of advanced neoplasia and CRC.Colorectal cancer (CRC) is one of the predominant cancers, contributing to a high burden of morbidity and mortality in the United States of America and Europe. 1,2 Early detection and treatment are critical factors in the course and prognosis of CRC, and screening programs have proven to be an important means to reduce both mortality and secondary economic burden. [3][4][5] Colonoscopy is considered the gold standard for CRC and advanced adenoma screening. Fecal immunochemical tests (FIT) are currently the most commonly used non-invasive fecal screening tests. However, sensitivity of FIT for CRC is between 66-88% 6-10 depending on the cut-off values used, whereas sensitivity for advanced adenomas is disturbingly low (27-41%). 6,8,11,12 As CRC prevention programs should primarily focus on early detection of premalignant advanced adenomas, the search for novel, more accurate non-invasive screening methods remains warranted.Analysis of volatile organic compounds (VOCs) in exhaled breath has been reported as a potential non-invasive diagnostic biomarker test for lung cancer, breast cancer, malignant melanomas and CRC. [13][14][15] VOCs are gaseous carbon-based chemicals resulting from biochemical processes in the body, which are discharged by exhaled air, sweat, urine and feces. 16 VOCs in fecal gases are mainly produced by the intestinal microbiota in the colon...