In this paper we present the results of studies on the susceptibility to antibiotics of bacteria isolated from chronic canine otitis externa. We tested 46 bacterial strains (S. aureus, coagulase-negative staphylococci, Corynebacterium spp., and gram-negative bacilli) with 20 different antibiotics. We observed increased resistance to antibiotics of bacteria isolated from canine otitis externa as compared to the resistance reported earlier. This may be due to the indiscriminate use of some antibiotics in the last years and indicates the importance of sensitivity testing for the effective treatment of chronic otitis externa, especially that caused by gram-negative bacilli. The clinician may initiate empiric treatment with antibiotics before obtaining the sensitivity test results; the best results may be expected from a topical application of Bacitracin or Chloramphenicol, and from a systemic therapy with Cephalosporines. Therapeutical scheme for treating various bacterial groups are presented in the paper.