Eighty-nine patients were studied for the incidence and nature of phantom breast sensations (PBS) after a modified mastectomy. Twenty-nine (33%) reported experiencing pain or itching in the breast or the more vague sensation that the breast was still present. Phantom breast sensations appeared generally within the first 3 postoperative months. The duration varies from a few seconds to a few minutes. There were great individual differences in the frequency at which PBS appeared. Forty-one percent had the experience monthly or more often. All of the patients with a high frequency of PBS (12) belonged to the group of 13 women who suffered under these sensations. The occurrence of PBS was not related to left or right mastectomy, radiotherapy, adjuvant chemotherapy, having a sexual partner, or a history of lactation. At the time of operation, women who later developed PBS generally were younger, premenopausal, more often had children, and had a preoperative history of breast sensations. Before the modified mastectomy, these four factors could be used to indicate the probability at which the woman would develop PBS.