The authors describe the case of a 24-year-old woman with valve disease. After a bout of respiratory tract infection, she was diagnosed to have bacterial endocarditis associated with mitral valve disease. The causative agents isolated included Eikenella corrodens, Streptococcus intermedius, Bacteroides oralis and Bacteroides bivius. At the same time, the patient was found to have developed IgA immunodeficiency. A complication accompanying the cardiac disease was spontaneous pneumothorax. Since antibiotic therapy had failed, the mitral valve was replaced by a prosthetic one. After the procedure, the patient had her teeth examined. The examination revealed complete destruction of tooth 36, thick layers of calculus and chronic gingivitis. E. corrodens was isolated also after microbiological examination of the patient's oral cavity. The reason for reporting on what we regard as an interesting case is that bacterial endocarditis with E. corrodens implicated as the causative agent is relatively rare; to date, polymicrobial endocarditis due to E. corrodens and other microorganisms has been described in intravenous drug addicts only.