Objective menstrual blood loss measurements (in ml) were compared with the score obtained from a pictorial blood loss assessment chart (PBAC) which took into account the degree to which each item of sanitary protection was soiled with blood as well as the total number of pads or tampons used. Twenty eight women used the chart during 55 menstrual cycles and a single observer assessed 122 cycle collections in a similar manner. A pictorial chart score of 100 or more, when used as a diagnostic test for menorrhagia, was found to have a specificity and sensitivity of greater than 80%. Demonstration of the relation between self assessed pictorial chart scores and the objective measurement of blood loss enables us to provide a simple, cheap and reasonably accurate method of assessing blood loss before embarking upon treatment.