Summary : Background : Colorectal cancer is the second commonest cause of cancer mortality. Some countries are implementing colorectal cancer screening to detect lesions at an early stage using non-invasive tools like the faecal immunochem. test. Despite affordability, this test shows a low sensitivity for precancerous lesions and a low pos. predictive value for colorectal cancer, resulting in a high false-pos. rate. Aim : To develop a new, non-invasive colorectal cancer screening tool based on bacterial faecal biomarkers, which in combination with the faecal immunochem. test, could allow a reduction in the false-pos. rate. This tool is called risk assessment of intestinal disease for colorectal cancer (RAID-CRC). Methods : We performed both the faecal immunochem. test and the bacterial markers anal. (RAID-CRC test) in stool samples from individuals with normal colonoscopy (167), non-advanced adenomas (88), advanced adenomas (30) and colorectal cancer (48). All the participants showed colorectal cancer-associated symptoms. Results : Performance of the faecal immunochem. test for advanced neoplasia (ie advanced adenoma and colorectal cancer) was determined by using the cut-off value established in Catalonia (20μg Hb/g of faeces) for a population-based screening approach. Sensitivity and specificity values of 83% and 80%, resp., and pos. and neg. predictive values of 56% and 94%, resp., were obtained. When both the immunol. and the biol. anal. were combined, the corresponding values were 80% and 90% for sensitivity and specificity, resp., and 70% and 94% for pos. and neg. predictive values, resp., resulting in a 50% reduction of the false-pos. rate. Conclusions : RAID-CRC test allows a substantial reduction in the faecal immunochem. test false-pos. results (50%) in a symptomatic population. Further validation is indicated in a colorectal cancer-screening scenario.