Mammographic density in digital mammograms can be assessed visuallyor using automated volumetric methods; the aim in both cases is to identifywomen at greater risk of developing breast cancer, and those for whommammography is less sensitive. Ideally all methods should identify the samewomen as having high density, but this is not the case in practice. 6422 womenwere ranked from the highest to lowest density by three methods: QuantraTM,VolparaTM and visual assessment recorded on Visual Analogue Scales. For eachpair of methods the 20 cases with the greatest agreement in rank were compared with the 20 with the least agreement. The presence of microcalcifications, skinfolds, suboptimally positioned inframammary folds, and whether or not the nipplewas in profile were found to affect agreement between methods (p