A total of 180 cases (contributing 404 serum specimens) and 532 controls (with 1180 specimens) were included in the study population. Eight cases could only be matched to 2 controls. Table 1 shows the distribution of cases and controls by demographic factors. Overall, about 83% were males, 49% were whites, 44% were blacks, over 57% were younger than 25 years, 10% were older than 35 years, about 12% were Hispanic, and over 56% were in the army. Approximately 35% of cases had greater than 3 years of military service.