To determine the incidence of the adult respiratory distress syndrome (ARDS) in Utah, we prospectively screened intensive-care-unit (ICU) patients for ARDS in six of the 40 general acute-care hospitals in Utah. Over a 1-yr period, we diagnosed severe ARDS (oxygenation criterion: PaO2/PAO2 < or = 0.2) in 110 patients. Of these patients, 27 were not residents of Utah. We estimated that there were 58 undetected Utah residents with ARDS in the remaining 34 Utah acute-care hospitals. We also estimated that one Utah resident per year received ARDS care outside Utah. Incorporating these two estimates, we calculated an estimated upper limit for ARDS incidence in Utah of 8.3 ARDS patients per 100,000 total Utah population per year. Using only directly identified Utah residents with ARDS, we calculated the absolute lower limit for ARDS incidence in Utah to be 4.8 ARDS patients per 100,000 Utah population per year. The incidence of ARDS in Utah is about an order of magnitude less than the 1972 National Heart and Lung Institute Task Force estimate of ARDS incidence in the United States, but agrees with more recently published ARDS incidence figures.