Nanotechnology is the engineering of functional systems at the molecular scale which may exert a revolutionary impact on cancer diagnosis and therapy. Nanotechnology is being applied to cancer in two broad areas: i) the development of nanovectors such as nanoparticles which can be loaded with drugs or imaging agents and then targeted to tumours, and ii) high-throughput nanosensor devices for detecting the biological signatures of cancer. Combined, such technologies could lead to earlier diagnosis and better treatment for cancer patients.