The study analyzed aggregated statewide data on arrests, license suspensions for DUI, and admissions to ADSAP for periods before and after the law's implementation. Case outcomes for samples of drivers apprehended for DUI before and after the law's implementation were also compared. DUI arrests were significantly higher after the law's passage than predictions based on previous arrest rates. The average blood-alcohol concentration of apprehended drivers also declined precipitately during this period, suggesting that the arrest increase resulted from increased enforcement rather than an increase in DUI. Data indicate, however, that the increased arrest rate was due more to public and police concern over DUI than to the new law. DUI convictions increased after the law, but less dramatically than the arrest increase. Admissions to ADSAP increased at a rate higher than that projected by prior admissions. Only about half of the sample apprehended for DUI in the fall of 1982 and subsequently convicted, however, had been admitted to ADSAP as of the fall of 1984. Additional research should determine why so many convicted of DUI did not enter ADSAP, given the law's mandate. Data figures and appended methodological discussions. (Publisher summary modified)