Sudden sensorineural hearing loss that presents as the initial sign of haematological disease is very rare. We report a case with typical Rai Stage 2 (Binet Stage A) CLL, who presented with sudden onset deafness as the initial manifestation. A 48-year-old male presented with sudden bilateral sensorineural hearing loss. The patient was found to have chronic lymphocytic leukemia (CLL) during a work-up for his hearing loss. Early onset of sudden deafness in a CLL patient may be due to the hyperviscosity syndrome. Audiograms were recorded showing positive findings on presentation and recovery after therapy. The importance of early diagnosis and therapy is stressed in the light of this rapid clinical and audiological recovery observed here. ©2007, Firat University, Medical Faculty