Phantom breast syndrome (PBS) following mastectomy has already been reported by other authors. The temporal course, character and extent of these phenomena, however, have not yet been elucidated. In a prospective study, we investigated the incidence, clinical picture and the temporal course of PBS. One hundred and twenty women who, during a 1 year period, embarked consecutively on post-operative control or treatment at the department, were interviewed by a standard questionnaire 3 weeks after the operation. One year later 110 patients were interviewed again. The median age at the first interview was 54 years (Q1 = 45 years; Q3 = 62 years). The incidence of PBS was 25.8% at the first interview and 24.5% at the second. The incidence of phantom pain and non-painful phantom sensations was 13.3% and 15.0%, respectively, 3 weeks after mastectomy and 12.7% and 11.8%, respectively after 1 year. We found significant relationships between pre-operative pain and PBS, but no significant relation between age and the occurrence of PBS. Neither post-operative sequelae nor cancer treatment including radiotherapy seemed to affect the occurrence of PBS. Exteroceptive-like pain emerged as the most predominant type of pain from both interviews. At the time of the first interview, 35.0% of the patients experienced cicatrix pain which was clearly distinguishable from phantom pain; after 1 year, 22.7% of the patients had persistent cicatrix pain. The present incidence of PBS is close to the incidence reported by others. Persistent phantom pain may, however, be more common than usually expected. Also persistence of cicatrix pain seems to be more common than generally expected.