The susceptibility of 29 strains of Eikenella corrodens to penicillin, apalcillin, and 12 new cephalosporins was determined by the agar dilution method. Most strains were resistant to cefsulodin, and some were resistant to apalcillin and cefpiramide. Although all strains were susceptible to the other cephalosporins tested, most of those drugs were as active as or less active than penicillin. Susceptibility testing of isolates should be performed whenever a cephalosporin is used to treat infections involving E. corrodens.