[en] Carcinomas of the prostate and breast are the most common sources of osteosclerotic metastases. The osteoblastic response is related to stromal bone formation and reactive bone formation. Purely osteosclerotic or mixed osteolytic-osteosclerotic lesions are encountered. Frequent differential diagnoses are enostoses and Paget's disease. The classical magnetic resonance imaging (MRI) pattern is a signal of low intensity but some osteoblastic metastases have an inhomogeneous signal. Evaluation of the response to treatment is difficult and requires confrontation with clinical and biological data. (authors). 61 refs., 11 figs., 2 tabs