Seventeen campylobacters isolated from cultures of blood samples of 16 bacteremic patients were susceptible to cephalothin and were either catalase negative or had only weak catalase activity (CNW strains) and were classified as "Campylobacter upsaliensis" (K. Sandstedt and J. Ursing, XIV Int. Congr. Microbiol., p. B8-17, 1986). All of the patients had predisposing conditions, and 10 patients were less than or equal to 12 months old, indicating that "C. upsaliensis" is an opportunistic pathogen of humans.