Disturbances associated with a breast cancer diagnosis were defined when psychological assessments from 63 patients with a known breast cancer diagnosis were compared to those from 56 patients with an as yet undiagnosed malignancy. Subsequent assessments from the 56 patients with an undiagnosed breast cancer showed disturbances after they saw a physician compared with the assessments from 72 similar patients ultimately diagnosed as benign. Apprehension apparently arose from clues given before a biopsy was done even though the cancer was not yet diagnosed. Compared with the benign breast disease group, the disturbances in patients suspected or diagnosed with breast cancer were found chiefly in assessments of mood and adjustment, and less in assessments of more durable characteristics of personality, psychopathology, and sexual behavior. Psychological problems associated with breast cancer decreased over time, but residuals persisted for at least 16 months postoperatively. Few differences were found between 41 patients who elected breast-conserving surgery and 78 who were treated with mastectomy. Problems were not eliminated by operations which saved the breast.