Background: Unplanned hospital readmissions after surgical treatment for breast cancer are an indicator of morbidity. We explore the relationship between the rate of unplanned hospital readmissions within 42 days of initial treatment and various factors, including tumor size and histology, lymph node involvement, type of surgical treatment, mastectomy, or breast-conserving surgery, and patient demographics. Methods: Linked Western Australian cancer mortality and hospital morbidity data were used in the assessment of readmissions within a period of 42 days after initial surgical treatment for breast cancer. Planned admissions for adjuvant treatment such as chemotherapy or radiotherapy were deleted. Survival models for multiple events per subject were applied to analyze the data. Results: The analysis reveals that patients more likely to experience lower recurrence of short-term unplanned hospital readmissions include those with smaller tumors, private insurance, and who reside in metropolitan areas. The model also includes important two-way interaction terms involving tumor histology, area of residence, and surgical treatment, and between lymph node involvement and patient age. Conclusions: This study suggests that the choice of breast-conserving surgery as a treatment for breast cancer does not invariably result in better postoperative morbidity, but rather, that other factors, including tumor size and patient demographics, play a critical role in the short term. These results differ from a previous study of longterm hospital readmissions-country of birth and method of payment were found to be associated with short-term hospital admission but not with longterm readmissions.