Mammography equipment must be assessed regularly to ensure that images will be of acceptable diagnostic quality with keeping radiation dose as low as reasonably practicable. Quality Assurance (QA) aims to provide systematic and constant improvement through a feedback mechanism to address the technical, clinical and training aspects (Reis et al., Insights Imaging, 4(5), 539–553, 2013; Andolina and Lillé, Mammographic imaging: a practical guide, 2011). Quality Control (QC), in relation to mammography equipment, comprises a series of tests to determine equipment performance characteristics. The introduction of digital technologies promoted changes in QC tests and protocols and there are some tests that are specific for each manufacturer (Andolina and Lillé, Mammographic imaging: a practical guide, 2011). Within each country specific QC tests should be compliant with regulatory requirements and guidance (Reis et al., Insights Imaging, 4(5), 539–553, 2013). Ideally, one mammography practitioner should take overarching responsibility for QC within a service, with all practitioners having responsibility for actual QC testing. All QC results must be documented to facilitate troubleshooting, internal audit and external assessment (IAEA, Quality assurance programme for digital mammography, 2011; Perry et al., Ann Oncol, 19(4), 614–622, 2008). Although tests can vary from country to country, and manufacturer to manufacturer, the main principles of system quality that are assessed during mammography QC are: contrast resolution, spatial resolution, noise, and radiation dose. All parameters are assessed to ensure that measurements are not deviating from when the machine was commissioned. This chapter aims to provide a clear summary of image quality, system optimisation and quality control for the practitioner.