Objective: This study examined whether offering annual mammography screening for women with the risk factor of a family history of breast cancer resulted in more favorable prognostic indicators of diagnosed cancers than the usual approach of biennial screening. Methods: The study involved women aged 50-69 years with a family history of breast cancer, defined as having ≥1 first-degree relative diagnosed with breast cancer, who were diagnosed with a screen-detected invasive breast cancer between 1998 and 2004 in BreastScreen New South Wales (n = 590). The women were grouped according to whether they screened in an area offering annual screening to women with a family history, or were offered the standard biennial screening. The odds of having favorable tumor size, grade, and nodal status prognosis were compared between these screening groups using logistic regression. A comparison group of women without a family history, all offered biennial screening, was also evaluated based on the same area groupings to examine whether any differences were due to the area, rather than the screening interval policy. Results: Women with a family history who were offered annual screening at BreastScreen NSW were significantly more likely than those who were offered biennial screening to be diagnosed with a tumor ≤20 mm in size (adjusted odds ratio (AOR) = 1.91, 95% CI: 1.21-3.02), and to have a node-negative tumor (AOR = 1.61, 95% CI: 1.03-2.50). There were also significantly higher odds of being diagnosed with tumors ≤15 mm (p < 0.001) and ≤10 mm in size (p = 0.011) in women offered annual screening. There was no significant difference in the odds of a Grade 1 tumor being detected (AOR = 1.26, 95% CI: 0.87-1.81), although the direction of the effect was consistent with that seen for size and nodal status. No significant differences were found in the comparison group of women without a family history. Conclusions: Offering annual screening for women aged 50-69 years with a family history of breast cancer significantly increased the odds of being diagnosed with a smaller, node-negative tumors. Further investigation is required to assess whether the improved prognostic indicators translate into significantly better mortality outcomes for women with a family history offered annually screening. © 2008 Springer Science+Business Media B.V.