The aim of the study was to determine if there is a relationship between the stage of breast cancer at the time of detection and the costs of treatment and to assess whether any such relationship would have an influence on the cost of a mammographic screening programme. A retrospective analysis of the stage at presentation for primary breast cancer and the treatment costs over the duration of treatment was made. Multiple regression analysis was employed, with treatment cost as the dependent variable and categorical variables to represent stage at detection. A total of 301 women whose treatment for breast cancer commenced at the Royal Brisbane Hospital participated in the study. A statistically significant relationship was found between the stage of disease at the time of detection and subsequent treatment costs; more advanced stages of disease incurred higher treatment costs. This relationship was robust even after taking into account the age of patients, their discharge status, and differences between patients in the duration of treatment. When the effect of earlier detection on treatment cost was assessed in relation to a breast screening programme, cost savings were estimated to be in the range of 8-36% of total screening costs. There are treatment cost savings to be gained from breast cancer screening as a result of the detection of earlier stages of disease. These treatment cost savings should be offset against the cost of a mammographic screening programme.