132 solid breast masses have been examined at our institution by MR and have consequently been histopathologically correlated. T1- and T2-weighted SE and multi-echo sequences have been evaluated visually. It was found that signal intensities of tissues on T2-weighted images correlated with the contents of fibrosis, cells or water. Thus in some lesions (which consisted of different tissue components), a characteristic internal structure was visible on T2-weighted images, reflecting their histopathologic structure. Corresponding to their different composition, differences of signal intensity have also been noted between those fibroadenomas with a high contents of fibrosis and all other well-circumscribed breast lesions (fibroadenomas, carcinomas). However, for the majority of lesions with irregular contours a discrimination based on signal intensities or calculated T1- and T2-values did not seem possible. This overlap can also be explained by the macroscopically similar composition (amount of fibrosis, water or cells) of benign and malignant irregular lesions.