Peritonsillar abscess occurs when bacterial infection of the tonsil spreads to the potential peritonsillar space deep behind the tonsil, and which is not rarely experienced in the otolaryngologic field in spite of decreasing incidence substantially since the advent of antibiotic therapy. A clinical observation was perfermed on 92 cases with peritonsillar abscess, who visited to Department of E.N.T. College of Medicine, Kyung Hee University during the past 5 years from June, 1978 to May, 1983. The obtained results were as follows ; 1) Male to Famale ratio was 1.3 to 1. 2) It was most frequently affected in the third decade showing 38 cases. 3) It was most frequently found in spring (37.0%), and summer, autumn and winter are next in order. 4) The duration from onset to visit was 5.5 days in average. 5) Right side was more frequently affected than left side (52 : 38). 6) The recurrent history of the peritonsillar abscess was found in 8 cases (8.5%). 7) The major symptoms were sore throat in 92 cases (100%), swallowing difficulty in 87 cases (94.6%), trismus in 87 cases (94.6%), fever in 72 cases (78.3%). And others were fatigability, dysarthria and etc. 8) Among 46 cases of the peritonsillar abscess, pathogenic organisms were isolated in 31 cases (67.4%), consisting of 11 cases of single infection and 20 cases of mixed infection, and not isolated in 15 cases (32.6%). 9) Among isolated 56 strains, α-hemolytic streptococcus were 21 strains (37.5%), β-hemolytic streptococcus 18 strains (32.1%), Staphylococcus aureus 9 strains (16.1%), Neisseria catarrhalis 7 strains (12.5%) and Pseudomonas aeroginosa 1 strain (1.8%). 10) All patients were satisfactorily treated with administration of parenteral antibiotics in addition of incision and drainage.