Abstract: A method of, and apparatus for, identifying human tissue which is suspected of being physiologically changed as a result of commencement of neoplastic activity or pre-activity, is disclosed. The tissue is preferably irradiated with light at wavelengths of 660 nm and 940 nm. The magnitudes of the reflected, or non-absorbed, light at the two wavelengths is compared, preferably after being normalized by the magnitude of ambient light reflected from the tissue immediately prior to each measurement. The invention finds application in detecting cervical lesions but is also applicable to endoscope inspectable tissues such as the lungs and alimentary canal tissues.