In this report we describe the MR imaging findings, including dynamic data, in a patient with primary non-Hodgkin's lymphoma of the breast. The precontrast T1-weighted sequence showed several hypointense, ill-defined, non-spiculated masses. In the T2-weighted images the masses showed a hyperintense halo. In the dynamic and postcontrast sequences all lesions enhanced markedly, and a further large mass was discovered. In comparison to mammography and sonography, only MR imaging identified the multicentric extent of the tumour. Differentiation from invasive cancer, based on either MR or conventional imaging features, was not possible.