A clinical scale, the Acoustic Neuroma Suspicion Index (ANSI) is presented. It was based initially on the retrospective analysis of 397 patients suspected of having an acoustic neuroma of whom, following full investigation, 263 (66%) were found to have space occupying lesions. After minor modifications, the Index was re-tested on 98 patients of whom 56 proved to have tumors while 47, who did not, formed a control group. All tumor cases were confirmed surgically. Neuro-otological investigations can be expensive, time consuming and occasionally unpleasant for patients; furthermore they are not always readily available. Though the diagnosis of an acoustic tumor or other cerebellopontine angle lesion is often straightforward, atypicality of presentation occurs often. The ANSI uses simple selected data from the history and clinical examination, with routine audiological, vestibular and radiological investigations to calculate a score. If this score exceeds the predetermined threshold, further investigations should be undertaken.