Abstract: Infrared spectroscopy of human stool can be used as a non-invasive method of detecting the presence of colorectal cancer and/or clinically significant adenomas. The spectrum of a patient's stool is compared with that of stool from non-cancerous subjects, observed differences in spectra being indicative of cancer and/or clinically significant adenomas. In a preferred method, the stool sample is mixed with a buffer, the resulting suspension is centrifuged and the supernatant is subjected to infrared spectroscopy. The spectra are then classified using a three-stage classification strategy.