The frequency of problems in the arm affected by surgery for breast cancer and the association of these problems with psychological distress were assessed among 223 women with newly diagnosed breast cancer 3 months after operation and again 15 months later among 201 of these same women. At 3 months after operation, 182 (82%) of the 223 patients reported at least one arm problem. Specific problems reported were swelling (24%), weakness (26%), some limitation in range of movement (32%), stiffness (40%), pain (55%) and numbness (58%), and these percentages had changed little 15 months later. Regardless of the type of mastectomy, women who underwent axillary dissection had more arm problems. Compared with women reporting no arm problems, the adjusted odds ratios of having psychological distress at 3 months for women reporting one to two, three to four and five to six arm problems were 1.2, 2.3 and 3.1 respectively (chi 2 for trend = 9.5, p = 0.002). Arm problems are frequent after operation for breast cancer, and these problems appear to increase the likelihood of psychological distress. Women should be informed that arm problems are expected but non-threatening sequelae of initial surgical treatment for breast cancer.