Breath alcohol ignition interlocks are the only system currently in use and the only system for which costs and benefit can be accurately estimated. An interlock prevents a vehicle from starting unless the driver's breath alcohol concentration is lower than a preset limit, typically .02 or .025. Substantial research shows that breath alcohol interlocks reduce the occurrence of arrests for driving while intoxicated (DWI) for selected groups of offenders compared to similar DWI offenders without interlocks (Beirness and Marques, 2004; Willis, Lybrand, and Bellamy, 2004); however, the beneficial effect dissipates once the interlock is removed. Thus, current use of this type of system is not apparently rehabilitation, only restrictive. Expanded use of these devices (fewer than 10 percent of convicted DWI offenders currently use interlocks), when coupled with close monitoring and supervision, would likely produce reductions in crash rates of habitual DWI offenders while the interlocks are on their vehicles. Alternative alcohol measurements technologies have potential for future use with DWI offenders and may offer some benefits over breath alcohol measurement. In addition to breath sample analysis, the technologies discussed in this report are tissue spectroscopy, transdermal perspiration measurement, eye movements, detection of alcohol vapor in the vehicle, and driver and driving performance measurement. A government-industry cooperation research program is in the process of being formed in order to conduct research and development of in-vehicle alcohol detection technology. 1 figure and 21 references