Multiple imaging modalities have been used in evaluating patients suspected of breast cancer. Mammography and ultrasound are the dominant modalities now used by most mammographers. Mammography has been shown to be inaccurate in patients with dense breast or in breasts where significant architectural distortion has occurred. Alternative modalities independent of breast density are currently being evaluated. These include ultrasonography, magnetic resonance imaging, and nuclear medicine techniques. Recent reports indicate methoxyisobutylisonitrile (MIBI) to be promising in the evaluation of patients with difficult to evaluate mammograms. The current sensitivity and specificity figures for MIBI scintigraphy of the breast are dependent on a number of factors. A recent multicenter trial involving 673 patients sponsored by the DuPont-Merck Radiopharmaceutical Corporation indicated an overall sensitivity of 85% with a specificity of 81%. Nonpalpable lesions showed a sensitivity of 55% to 72%. The acceptance of MIBI breast imaging will be dependent on specific applications in which MIBI can be shown to be superior to alternative modalities. A promising subgroup of patients includes patients with dense breasts, breasts with architectural distortions, or extensive scaring from prior biopsies, especially if these patients are considered to be in a high risk category.