The objectives of modern otologic surgery are elimination of disease and restoration of hearing. Persistent drainage and recurrent infection after mastoid surgery hallmark failure at achieving these goals. Medical management consisting of meticulous aural toilette and attention to accompanying medical disorders will often yield resolution; however, a significant number of patients will still require surgical revision. While intact canal wall procedures have reduced the chronic difficulties associated with open cavities, they are prone to failure. Careful assessment of the disease process and development of a surgical approach that is both flexible and complete will maximize success in revision surgery. Disease persistence after revision should be considered in the spectrum of complications, even though at times it is nearly impossible to avoid. We describe the reasons for failure of mastoid procedures, common areas of retained disease, and review key concepts of revision.