PURPOSE: To assess possible changes in quality control (QC) practices at mammography sites in the United States. MATERIALS AND METHODS: Mammography site surveys were conducted in 1990, 1992, and 1995 through the Colorado Mammography Advocacy Project (CMAP). Data from mammography sites applying for American College of Radiology (ACR) accreditation were collected between August 1987 and August 1993 through the ACR. Mammography Accreditation Program Data from both of these surveys were analyzed to assess temporal changes in mammography QC practices in the United States between 1987 and 1995. RESULTS: CMAP results indicated statistically significant improvement in medical physicist QC practices between 1990 and 1992 and in technologist QC practices between 1990 and 1995. Improvements in radiologic technologist QC practices coincided with increases in radiologic technologist continuing education in mammography ACR results indicated statistically significant improvement in technologist QC practices between 1988 and 1992. CONCLUSIONS: There have been substantial improvements in QC practices at mammography sites in the United States during the past decade.