Background: This trial examines the utility of breast magnetic resonance imaging (MRI) for detection of occult breast disease and its effect on surgical treatment.Methods: Between October 2000 and March 2002, 76 of 1,289 patients underwent bilateral breast MRI within 4 months of a mammogram. The MRI scan, mammogram, pathology reports, and physicians' notes were reviewed to determine impact of MRI on surgical treatment.Results: Magnetic resonance imaging detected 23 additional lesions in 19 patients not detected by mammogram. Cancer occult to mammography was detected by MRI in 6 women, constituting 7.9%. Magnetic resonance imaging impacted surgical treatment plans in 10 of 76 (13.2%) patients.Conclusions: Magnetic resonance imaging is effective at identifying new subclinical breast disease not seen on mammography. Ten of 76 patients (13.2%) who underwent MRI had their surgical management altered due to MRI findings. Specific criteria should be studied to know which subgroups would benefit most from breast MRI. (C) 2003 Excerpta Medica, Inc. All rights reserved.