Magnetic resonance imaging (MRI) is the modality of choice in the diagnosis of pituitary pathology. A chronological outline and discussion of the radiological classifications of pituitary adenomas applied so far are presented, with a review in depth of the up-to-date classifications based on MRI. SIPAP is an MR classification used in Scandinavia. It is basically a six-figure number describing the extrasellar extension of the adenoma. Together with tumour size, it is a useful and simple method for registration of pituitary adenomas.