When established in 1976, ARJIS was designed to assist in the identification and apprehension of suspected criminals by increasing the exchange of information among San Diego County, Calif., law enforcement personnel. As originally designed, the system contained the Master Operations Index, which integrates the crime case, arrest, suspect, and property files; and personnel; automated worthless document; crime analysis; and manpower allocation components. Parts of the system are still not developed, others are being changed, and some are not being used by all agencies, so that the full impact of ARJIS cannot be measured. Since November 1980, the use of ARJIS has increased, as have the benefits received in terms of arrests and crime cases cleared with ARJIS information. The effectiveness of ARJIS is expected to increase if officers receive additional training in data access, the quality of information is improved, components are fully used by all law enforcement agencies in the region, and proposed development and enhancement of the system occur. During the next year, careful monitoring should be conducted and periodic reports submitted to the ARJIS board to ensure that the problem areas are being addressed. These reports should also include cost assessments compared to benefits received. Findings suggest cost savings associated with ARJIS, but whether savings will outweigh the expenditures when the system is fully operational is not known. (Author abstract modified)