Because no perfect measure of firearm availability exists, the CHD intends to link several indicators from diverse public health and public safety sources to produce a measure of firearm availability that can be used to predict and prevent lethal violence in small areas of Chicago. The CHD contains information on every homicide in police records from 1965 to 1994, nearly 23,000 homicides. Unburdened by many of the limitations inherent in statistics such as Supplementary Homicide Reports in Uniform Crime Reports, the CHD is organized so that questions about victims, offenders, and incidents can be answered. Based on the CHD, a firearm availability project has been initiated to integrate homicide data with an address-based measure of firearm availability by firearm type. The goal is to relate firearm availability to firearm deaths in specific Chicago neighborhoods in order to explain the escalation in homicide levels. 6 references and 3 figures