Peritonsillar abscess, or ""Quinsy"" was a source of morbidity and mortality in patient prior to the advent of antibiotics. Although the incidence of this condition has decreased substantially since the advent of antibiotic therapy, peritonsillar abscess is not rare and frequently encountered in clinical field. A clinical observation was performed on 75 cases with peritonsillar abscess, who visited to Department of Otolaryngology, College of Medicine during past 10 years from November, 1973 to October 1982. The obtained results were as follows ; 1) The incidence of peritonsillar abscess in former 5 years was 0.119% latter 5 years was 0.067%. 2) Male to Female ratio was 7 to 8. 3) Third decade 30 cases(40%) were most frequently affected. 4) It was most prevalent in autumn 27 cases(33%), summer, winter and spring are next in order. 5) The mean duration from onset to visit was 6.4 days. 6) Site of the abscess was right 34 cases(45.3%), left 38 cases(50.7%), both 2 cases(4.0%). 7) The most frequent clinical manifestation were sore throat in 75 cases(100%), swallowing difficulty with drooling 70 cases(93.3%), trismus 70 cases(93.3%), fever 52 cases(70.6%). 8) Among the 75 cases, most frequent temperature of patient at visit was 37.5-38.5°C 40 cases(54.6%). 9) Among the 75 cases of peritonsillar abscess, 40 cases were pus cultured and pathogenic organisms were isolated 28 cases(70%), consisting of 10 cases of single infection and 18 cases of mixed infection ant not isolated in 12 cases(30%). 10) Among the isolated 50 strains, α-hemolytic streptococcus were 22 strains(44.0%), β-hemolytic streptococcus 19 strains(38.0%), Klebsiella 5 strains(10.0%), H. influenza 3 strains(6.0%), S. aureus 1 strains(2.0%). 11) All patients were treated with parenteral and oral antibiotics and incision and drainage were performed satisfactorily. 5 elective tonsilltomy and 2 immediate tonsillectomy were performed in recurrent peritonsillar abscess without complication.