The synthesis and antibacterial activity in vitro of the 2-aryl-2-hydroxyiminoacetyl cephalosporins (2) are described. Within this cephalosporin series, analogs (9f approximately 13f) with 2-hydroxyimino-2-(3-hydroxyphenyl)acetyl group at the 7-position of a cephem nucleus were found to have the highest antibacterial activity against a wide-range of microorganisms, including beta-lactamase-producing bacteria. Structure-activity relationships of 2 are discussed.