Trauma is a significant cause of premature death in developing nations, but financial resources to deal with it are extremely limited. To determine which segments of a developing nation's trauma system would be most amenable to improvements, we compared management and outcome of all seriously injured patients (Injury Severity Score of > or = 9 or died) treated over 1 year by the trauma systems associated with an urban hospital in Latin America, Regional Trauma Center 21 (n = 545) in Monterrey, Mexico, and a level I trauma center in the United States, Harborview Medical Center (n = 533) in Seattle, Wash. Mortality was higher in Monterrey (55%) than in Seattle (34%, p < 0.001), because of a preponderance of prehospital and emergency room (ER) deaths. In Monterrey, 40% of seriously injured patients died in the field and 11% in the ER, compared with 21% in the field and 6% in the ER in Seattle (p < 0.001). There were significant differences in prehospital care between the two trauma systems. Scene and transport times were < 30 minutes for 47% of Monterrey cases vs. 75% in Seattle (p < 0.001). For patients with arrival blood pressure < 80, prehospital intubations had been performed on 5% of Monterrey patients vs. 79% in Seattle (p < 0.001) and en route fluid resuscitation administered to 70% of Monterrey patients vs. 99% in Seattle (p < 0.001). The observed mortality patterns indicate that priorities for trauma system improvement in urban Latin America should focus on more rapid prehospital transport and improved en route and ER resuscitation.(ABSTRACT TRUNCATED AT 250 WORDS)