Heroine is synthetic derivative of morphine, a naturally occurring substance extracted from unripe seeds or capsules of Papaver somniferum (poppy plant). The use of heroine and morphine as a recreational drug has reached epidemic proportion, largely because of increased availability. The currently used techniques for the detection of opiate drugs are time consuming, expensive and not amenable to on-site application. This book describes about development of a highly sensitive, fast, reliable, field applicable and cost effective immunoassay/ immunobiosensor for the detection of opiate drugs: morphine and heroin, the most addictive and commonly abused narcotics. Various types of immunoassay are described in this book using enzyme, fluorophore, carbon nanotubes, gold nanoparticles and phage display detection which shows detection limit in the ppb range without the aid of any sophisticated instrument.