89 patients with chronic otitis media were random-sampled from the patients who were operated under the impression of C.O.M., but had persistent and profuse otorrhea despites the systemic administration of sensitive antibiotics and the postoperative local treatment. Culture study revealed 38 cases (35.5%) were due to Pseudomonas aeruginosa. This incidence was slightly higher than 18.4% in C.O.M. general. It indicates the facts that susceptible organisms were excluded during appropriate treatment. Sensitivity tests to antibiotics were taken in 38 patients with Pseudomonas. 77.5% were susceptible to Gentamycin, but almost all cases were resistant to other antibiotics. There were no differences between groups with pseudomonas and groups without Pseudomonas in history, physical findings, and incidence and severity of complications. Of the 38 cases with Pseudomonas infection, 18 cases were vaccinized with monovalent vaccines which were made from the organisms isolated from the patients themselves. Vaccination against Pseudomonas could shorten the clinical courses significantly between operations and clinical healings. There were no local or systemic reactions of vaccination except local indurations (100%) and mild fever (2 cases). If the vaccination were tried in patients with persistant & profuse otorrhea, or patients with Pseudomonas infections resistant to all antibiotics, it will be of value than other measures.