A patient may experience hallucinations in more than one modality simultaneously or at different times and they may or may not appear to emanate from a single source. Current nomenclature is imprecise, often has particular diagnostic implications and fails to distinguish between these different phenomena. This has resulted in considerable confusion with a tendency to dismiss the importance of these symptoms. The various terms in current usage and the presence of these symptoms in a variety of different conditions are examined. To aid further research and improve clinical practice the authors advocate the use of the term multi-modal hallucinations and suggest operational criteria.