Endoscopy has been used for the visualization of pathology in many surgical fields. Endoscopic removal of the chronic sinusitis is now a routine procedure in most otolaryngologic practices. Recently there have been several reports of using small endoscopes to evaluate middle ear pathology and endoscopy of the mastoid performed transcutaneously for the second look operation to rule out residual cholesteatoma. This endoscopic second stage operation offers several advantages over the standard operation. 1) The use of various angled lenses enhances visualization. 2) Reduced operation time. 3) Minimal pain, swelling or bleeding. 4) No auricular numbness or displacement. We found several advantages by mastoidoscopy for second look operation in the cases of residual cholesteatoma.