At Nhan Dan Gia Dinh hospital, we have 4 cases of recurrent fungal maxillary sinusitis though maxillary ostium was widened enough for ventilation purpose. A matter placed for revision surgery is that we must have a surgical method to irrigate and endoscopically check for lowest part of the sinus, ensure totally remove fungal mass and fungi - bearing allergic mucin, to avoid recurrence. Method: Case series.