In 1942, a forensic scientist recommended the Luminol test for use in forensic blood detection. His research showed that the older the stain, the longer and more pronounced the luminescence. Luminol is highly sensitive to blood, convenient to use, and nondestructive to other forms of blood testing. Large areas at crime scenes can be scanned using Luminol with no ill effects on blood. Blood stains are readily enhanced by Luminol which allows for an interpretation of blood stain patterns. A question associated with the use of Luminol, however, is with what other chemicals or substances Luminol reacts. For example, tests have shown that when an item having blood on it is cleaned with a heavy concentration of bleach, it gives off a negative response. When spraying an outdoor crime scene, several test areas should be sprayed first to see what kind of results can be anticipated with Luminol. Spraying a suspected area with Luminol will not affect any other testing needed on dried blood stains. Photography of chemiluminescence is described, and a case history involving the use of Luminol is included.