In this chapter, the condition called sudden sensorineural hearing loss, a medical emergency, is defined. The chapter outlines the specific history and examination of such patients with appropriate illustrations. The various causes for this condition are described and have been tabulated, keeping in mind that in the majority of instances the condition is idiopathic. A flow chart for arriving at a diagnosis of the cause of sudden sensorineural hearing loss based on history is included. The various associated symptoms and their significance are described. Relevant ENT examination to exclude a local cause is described in detail. Audiometric assessment, biochemical tests and radiological assessment which should be performed in these patients are described in detail. The timing of therapy and dose and duration of systemic and topical steroid therapy is described in detail. Adjunctive therapy has been described in detail. Poor prognostic factors are in this condition are also described.