In some patients with breast disease, mammography and ultrasonography can provide only limited diagnostic information. Magnetic resonance imaging of the breast has high sensitivity and specificity and can play a significant diagnostic role in problem situations. Patients who are most likely to benefit are those with (i) axillary adenopathy of unknown primary origin, (ii) possible tumour recurrence after surgery or radiotherapy, (iii) lesions overlying implants, or (iv) those requiring staging of lobular or multifocal carcinoma.