Certain strains of Shiga toxin-producing Escherichia coli (STEC) which do not have the locus of enterocyte effacement pathogenicity island carry the STEC autoagglutinating adhesin (saa) gene. The distribution of the saa gene in STEC isolates from patients with hemolytic-uremic syndrome (HUS), patients with less severe diarrheal disease, asymptomatic individuals, and healthy cattle was examined. saa-positive strains were detected more frequently (P < 0.001) in STEC strains from bovines (32 of 56 strains) than in those from humans (8 of 91 strains). No significant association (P = 0.135) was found between the saa gene and STEC isolated from patients with HUS (6 of 46 strains) or diarrhea (2 of 29 strains) and from healthy controls (0 of 16 strains).