Flemer et al. profiled the microbiota in oral swabs, colonic mucosa samples and stool from individuals with either colorectal cancer (CRC; n = 99), colorectal polyps (n = 32) or healthy individuals as controls (n = 103). They found that several oral taxa (such as Streptococcus and Prevotella spp.) were differentially abundant in CRC versus controls. Moreover, they developed a classification model based on oral swab microbiota that distinguished individuals with CRC or polyps from controls (sensitivity: 53% CRC, 67% polyps; specificity: 96%). Importantly, when data from both faecal and oral swab microbiota were considered in this model, the sensitivity increased to 76% for CRC and 88% for polyps, respectively. Finally, high abundance of Lachnospiraceae was negatively correlated with a Western diet and colonization of colonic tissue with oral bacteria (including oral pathogens associated with CRC), hinting at a possible protective role for certain microbiota types. The authors postulate that analysing the oral microbiome could be an alternative method to screening for CRC.