This descriptive population-based study estimates the incidence, and describes the management and outcomes for women diagnosed with gestational breast cancer (GBC) aged 15-44 years in Western Australia between January 1982 and December 2000.Gestational breast cancer accounted for 6.25% of breast cancers in Western Australian women less than 45 years of age, and complicated 23.6 per 100,000 pregnancies. Two thirds were diagnosed postpartum and a third while pregnant. The median time from first symptom to diagnosis was less than four weeks. Women diagnosed during pregnancy were more likely to have a pregnancy termination. Over 50% of women were lymph node positive and those diagnosed postpartum were more likely to have a mastectomy. Five-year survival was better than reported previously (73%).The incidence of GBC was lower than previously reported. Significant differences in pregnancy outcome and management exist between the pregnant and postpartum groups. (c) 2005 Elsevier Ltd. All rights reserved.