Six hundreds fifty two cases of chronic suppurative otitis media who had been taken middle ear surgery at Dept. of Otolaryngology, Seoul National University Hospital, during past 5 years (from Jan. 1969 to Dec. 1973) were evaluated and we report the results. The following results were obtained : 1) Male to female ratio was 1.4 to 1 and age distribution showed predilection for age of 20 to 29 with 282 cases (43.2%). 2) No significant difference in site incidence was noticed. 3) Subjective complaints in order of frequency were as follows : otorrhea 635 cases (97.2%), hearing loss 608 cases (93.2%), headache 354 cases (35.4%), vertigo 147 cases (22.5%), tinnitus 121 cases (18.6%) etc. 4) Duration of disease since onset, showed predilection for duration of 16 years to 25 years (44.3%). 5) The development of mastoid pneumatization in chronic suppurative otitis media was underdeveloped in 94.5% and well developed in only 5.5%. There appears bony destruction (cholesteatoma) in 22.7%. 6) Type of operation for middle ear surgery were radical mastoidectomy in 243 cases (37.3%), tympanoplasty mastoidectomy in 238 cases (36.5%), tympanoplasty only in 149 cases (22.9%) and others in 22 cases (3.3%). 7) Otorrhea positive at the time of operation was 79.2% and otorrhea negative was 20.8%. About 88% of otorrhea positive cases required mastoidectomy. 8) Condition of tympanic membrane at the time of operation in order of frequency were as follows : total defect 31.2%, large perforation 80.3%, small perforation 12.6%, obstructing granulation polyp 11.7%, pars flaccida perforation 8.8%. In cases of radical mastoidectomy high incidence was shown in total defect (41.5%) and obstructing granulation polyp (25.7%), and in cases of tympanoplasty only high incidence was shown in large perforation (38.1%) and small perforation (31.4%). 9) Incidence of cholesteatoma was revealed in 254 cases (40.4%). In the cases which was accompanied cholesteatoma, required radical mastoidectomy in 71.3%. 10) Rate of intracranial complication was 4% (26 cases), and the mortality rate was 23% (6 cases). The most frequent postoperative complication was facial nerve palsy and labyrinthitis, perichondritis in order. 11) The recurrence rate of otorrhea was 13.1% and cure rate was 86.9% suspected.