Salivary gland tumours are a relatively rare group of lesions best managed in specialist centres. We review some of the factors that influence their prognosis. Clinical stage is the most important, with large malignancies having a poor prognosis regardless of histological grade and other features such as perineural invasion. Even high grade neoplasms may do well when they are small. A helpful guide to the management of salivary cancers is the "4 cm" rule.