To clarify the postoperative complications of ethmoidectomy, a retrospective study was performed of 623 patients who underwent transantral, intranasal and external ethmoidectomy for chronic sinus diseases. The obtained results were as follows ; 1) 32 intranasal ethmoidectomy, 12 external ethmoidectomy and 932 transantral ethmoidectomy procedures were performed on 623 patients, which were 397 bilateral and 182 unilateral procedures. 2) Among the immediate postoperative complications, 508 patients(87.7%) suffered from some degree of facial swelling. 3) Recurrent polyps were noted in 35 patients(11.8%) in transantral ethmoidectomee group and 5 patients(20.8%) in intranasal ethmoidectomee group. 4) One patient died of cerebral injury in consequence of transantral ethmoidectomy procedure. 5) Higher rates of major complications have been observed in patients of previous nasal surgical histories and operations performed by residents than staffs. Each shows 20.4% and 10.9% differences, respectably(P<0.01). 6) Overall complication rates were 24.5% in transantral ethmoidectomee group, 20.8% in intranasal ethmoidectomee group, and 0% in external ethmoidectomee group.