Retropharyngeal abscess is reported to be decreasing in frequency in recent years. We report two cases of retropharyngeal abscess that were diagnosed within four years in Department of Otorhinolaryngology, Gifu University Hospital. Case 1 was a 36-year-old male who was suggested to have an abscess as primary infection and case 2 was a 71-year-old female whose abscess seemed to be a secondary infection following unknown primary infection. Endoscopic or open neck drainage as well as antibacterial chemotherapy mainly with combinations of flomoxef and clindamycin in the case 1 and piperacillin and clindamycin in the case 2 was successfully carried out. They were discharged an 15-day and 24-day after operation in the cases 1 and 2, respectively. A 30 min. culture after sample collection on operation demonstrated aerobe-anaerobe mixed infection in both cases; three aerobes and four anaerobes in the case 1 and three aerobes and two anaerobes in the case 2. These results suggest that retropharyngeal abscess may be a complicated infection involving more bacterial species than has been commonly believed. Measuring susceptibility of isolates to antimicrobial agents, a strain of Capnocytophaga sp. and a strain of anaerobic gram-negative rod were highly resistant to piperacillin, cefroxine and ofloxacin. It is important for adequate antibacterial chemotherapy to grasp the bacteriology of retropharyngeal abscess and analyze susceptibility of antimicrobial agents.