OBJECTIVE: To compare how frequently selected chronic diseases developed in women with breast cancer receiving endocrine therapy, and in women without cancer. DESIGN, SETTING AND PARTICIPANTS: Retrospective, rolling cohort study, analysing a random 10% sample of Pharmaceutical Benefits Scheme (PBS) data for the period 1 January 2003 - 31 December 2014. Women with breast cancer who first commenced endocrine therapy between January 2004 and December 2011 were identified, and age- and sex-matched (1:10) by comorbidity with control groups of women who did not have a dispensing record for antineoplastic agents during the study period or the comorbidity of interest at baseline. MAIN OUTCOME MEASURES: Development of any of eight pre-selected comorbidities, identified in PBS claims data with the RxRisk-V model. RESULTS: Women with hormone-dependent breast cancer were significantly more likely than women in the control group to develop depression (overall hazard ratio [HR], 1.36; 95% CI, 1.26-1.46), pain or pain-inflammation (HR, 1.30; 95% CI, 1.23-1.38), osteoporosis (overall HR, 1.27; 95% CI, 1.17-1.39), diabetes (HR, 1.24; 95% CI, 1.10-1.41), cardiovascular disorders (overall HR, 1.22; 95% CI, 1.13-1.32), and gastric acid disorders (HR, 1.20; 95% CI, 1.13-1.28). The hazard ratios for developing cardiovascular disorders, depression and osteoporosis were highest during the first year of endocrine therapy. The risk of hyperlipidaemia was lower among women with breast cancer than in the control group (HR, 0.88; 95% CI, 0.81-0.96). There was no significant difference between the two groups in the risk of reactive airway diseases (HR, 1.05; 95% CI, 0.98-1.13). CONCLUSION: Comorbid conditions are more likely to develop in women who have been diagnosed with hormone-dependent breast cancer than in women without cancer. Our results further support the need to develop appropriate models of care to manage the multiple chronic disorders of breast cancer survivors.