Renal and adrenal anatomy, both normal and abnormal, are well depicted by MRI Although MRI is not a sensitive modality for detection of renal cell carcinoma, it has clinical utility for evaluation of vascular involvement or direct extension of neoplasm into adjacent organs when CT findings are equivocal. Use of signal characteristics has not been useful in differentiating simple from complex cystic renal masses or among the various causes of medical renal disease and renal transplant failure. Similarly, signal characteristics are not sufficiently reliable for differentiating benign from malignant adrenal masses. MRI is useful, however, for detection and localization of pheochromocytomas. MRI plays a major role in imaging of children with neuroblastoma and Wilms' tumor and may obviate other, often more invasive, examinations in these cases.