The detection of breast cancer relies on high-quality images fromdigital mammography. Optimal levels of compression force are unknown, andUK national guidelines recommend forces of less than 200N. However, largevariations in compression forces exist and may be influenced by the mammographypractitioner and the breast size and pain threshold of the patient. Thisstudy examined the relationship between breast density and compression force.Women attending for routine breast screening and who had a mammogram takenby the same practitioner on the same equipment were included in the study(n=211). Volumetric density measurements were obtained using Volpara™ anddetails on imaging parameters were obtained from the DICOM headers. Therewas a strong, positive correlation between compression force and fibroglandulartissue. There was also evidence of a significant positive association betweencompression force and breast volume which was independent of the volume offibroglandular tissue present.