Previous studies have demonstrated an increased risk of breast cancer among patients with systemic sclerosis (scleroderma). To describe the clinical characteristics of 21 patients with both systemic sclerosis and breast cancer, and compare their risk factors to female scleroderma patients without breast cancer, in a population-based cohort study of South Australia. Subjects with scleroderma and breast cancer were identified from the South Australian Scleroderma Register with cross-linking to the South Australian Cancer Registry, last updated to the end of December 2005. Clinical information was obtained from standardised self-administered questionnaires and case note reviews. Odds ratios for the risk factors for breast cancer in scleroderma were determined, and clinical variables were analysed using chi square, Fisher's exact, Mann-Whitney and t tests. At the end of December 2005 there were a total of 389 female patients with scleroderma. Of these, 21 (5.4%) had been diagnosed with breast cancer. The mean age of onset of scleroderma was 43.5 years, and the mean age of breast cancer was 60.5 years in those with scleroderma and breast cancer. The majority (71.4%) had limited scleroderma, with anti-centromere antibody being the most prevalent serological abnormality. In 16 (76%) patients the diagnosis of breast cancer occurred on an average of 22.3 years after the onset of their first scleroderma symptom. When compared to 48 controls, scleroderma patients with breast cancer were found to have a higher incidence of a positive family history of breast cancer (Fisher's exact test, p = 0.04) and a lower incidence of hormone-replacement therapy use (Fisher's exact test, p = 0.0026). This population-based cohort study provides evidence that the majority of patients with scleroderma and breast cancer have limited scleroderma and anti-centromere antibody. Given the increased incidence of solid tumours in systemic sclerosis, we suggest regular screening of female patients for breast cancer, especially in those with a family history.