This article was presented at the conjoint CSSA and RACS (colorectal section) spring meeting Queensland, Australia, September 2004. The adenoma-carcinoma sequence describes a succession of events from polypoid adenoma to colorectal cancer. However, this model only accounts for up to two-thirds of colorectal cancers. There is growing evidence that flat adenomas are precursor lesions to a flat type of colorectal cancer and certain subtypes of these polyps are at greater risk of malignant transformation. If confirmed, the implications for screening, endoscopic recognition and management will become of increasing importance if we are to decrease the incidence of colorectal cancer.