Abstract Background Optical techniques using previously unexploited properties of light interaction with tissue may be valuable in the detection, diagnosis and staging of colorectal neoplasia. Methods A Medline search (1990 to present) was conducted on optical diagnostics in the detection of colorectal neoplasia. The reference list of each identified article was reviewed for further relevant papers. Results and conclusion Chromoendoscopy is the only optical adjunct to colonoscopy that has been tested in large randomized clinical trials. It improves the detection of small and flat colorectal adenomas, and of neoplasia in chronic ulcerative colitis and hereditary non-polyposis colorectal cancer. All other techniques are the subject of ongoing research and the practicality of population screening with any of the methods has yet to be established. Optical techniques may, however, permit immediate clinical diagnosis, removing the need for histological analysis. They may also improve the diagnosis of early colonic neoplasia.