Purpose: Some women with unilateral ductal carcinoma in situ (DCIS) undergo contralateral prophylactic mastectomy (CPM) to prevent cancer in the opposite breast. The use and trends of CPM for DCIS in the United States have not previously been reported. Methods: We used the Surveillance, Epidemiology, and End Results database to analyze the initial treatment (within 6 months) of patients with unilateral DCIS diagnosed from 1998 through 2005. We determined the CPM rate as a proportion of all surgically treated patients and as a proportion of all patients who underwent mastectomy. We compared demographic and tumor variables in women with unilateral DCIS who underwent surgical treatment. Results: We identified 51,030 patients with DCIS; 2,072 patients chose CPM. The CPM rate was 4.1% for all surgically treated patients and 13.5% for patients undergoing mastectomy. Among all surgically treated patients (including breast-conserving surgery), the CPM rate increased by 148% from 1998 (2.1%) to 2005 (5.2%). Among patients who underwent mastectomy to treat DCIS (excluding patients undergoing breast-conserving surgery), the CPM rate increased by 188% from 1998 (6.4%) to 2005 (18.4%). Young patient age, white race, recent year of diagnosis, and the presence of lobular carcinoma in situ were significantly associated with higher CPM rates among all surgically treated patients and all patients undergoing mastectomy. Large tumor size and higher grade were significantly associated with increased CPM rates among all surgically treated patients but lower CPM rates among patients undergoing mastectomy. Conclusion: The use of CPM for DCIS in the United States markedly increased from 1998 through 2005.