An estimated 3.6 million workers aged >/= 15 sought medical treatment in a hospital emergency department (ED) for an occupational injury or illness in the United States during 1998, as measured by a national probability , sample of hospitals. Ninety-eight percent of the workers were discharged from the ED, while 2% (77,246 +/-19,190, 95% confidence interval) were hospitalized for additional medical care. Workers hospitalized show significant differences (p<0.01) by sex, age, and injury demographics compared to the ED-discharged. Hospitalized patients were 85% male (65,571+/-16,582) and 15% female (11,675+/-3,397), whereas the ED-discharged were 70% male and 30% female. The hospitalized age-specific incident rates were higher among older patients, 10.4/10,000 workers for ages >/= 60 years compared to 6.2 for the <60. The ED-discharged incident rates steadily decreased with age. Injuries to the head, upper trunk/chest, and leg regions among the hospitalized showed more than a 2-fold increase in the proportion of cases, while amputations increased 14-fold, fractures 7-fold, and blunt head trauma 4-fold. By type of incident, falls from height accounted for 19% of the hospitalized cases, with falls from roofs increasing 19-fold, scaffolding 9-fold, and ladders 4-fold. Caught or compressed in equipment accounted for 12% of the hospitalized cases. Atypical chest pain (3%) and pedestrians struck by vehicles (2%) proportionately increased 14- and 7-fold. In conclusion, prevention of hospitalized nonfatal work events should focus in areas such as fall protection and machine guarding, similar to fatal prevention rather than areas dictated by most nonfatal incidents.