Abstract Aim: To identify the magnetic resonance (MR) morphological and enhancement characteristics of the normal and diseased nipple. Materials and methods: The MR appearances of the nipple in 35 patients with known primary breast cancer who went on to mastectomy was reviewed by two radiologists (blinded to the clinical, mammographic and histopathological information) and correlated with histology. The appearance of the contra-lateral nipple in 31 patients was reviewed and compared with that of the affected side. MR was performed at 1.0T using a receive-only double breast coil in 33 patients and a single breast coil in two patients. Three dimensional (3-D) T1-weighted gradient-echo images were made before and immediately after a fast hand injection of gadolinium-DTPA (0.1 mmol/kg). Results: Twenty-six breasts had histopathologically normal nipples and retroareolar tissue, four had evidence of tumour within the nipple and four had retroareolar tumour but with nipple sparing. Fifteen normal nipples were everted and 11 were inverted (flat). All showed superficial linear dermal enhancement above a non-enhancing zone in the nipple areolar complex. Linear or patchy enhancement deep to the non-enhancing zone was seen in four breasts and linear enhancement through the non-enhancing zone was seen in two. The nipple in all four breasts with tumour involvement showed increased thickening/bulkiness and enhancement of the nipple-areolar complex and retroareolar tissue. The four breasts with retroareolar tumour and nipple sparing showed increased thickening and enhancement of the retroareolar tissue only. There was one false positive result on breast MR for retroareolar tumour involvement. In this case the abnormally enhancing retroareolar tissue adjacent to the focal mass was shown to be an area of sclerosing adenosis on histology. The 31 contra-lateral nipples had the characteristic ‘normal’ appearance and when compared with its normal ipisilateral nipple showed marked symmetry. When compared with its abnormal ipsilateral nipple showed marked asymmetry. Conclusion: MR of the breast can show nipple involvement even when clinically unsuspected. This is important for treatment planning of breast cancer, in particular nipple preserving surgery.