Fulvestrant, which degrades ER, is used after aromatase inhibitor (AI) failure in metastatic breast cancer but resistance develops quickly. We hypothesized that using everolimus to inhibit mammalian target of rapamycin (mTOR), a key signaling pathway in endocrine resistance, may delay fulvestrant resistance in patients and thus improve its efficacy. We conducted a phase II trial of combined fulvestrant and everolimus in postmenopausal women with disease progression or relapse after an AI. Primary endpoint was time to progression (TTP) and secondary endpoints included objective response rate, clinical benefit rate (CBR), safety, and biomarker correlates. Tumor blocks were collected and biopsy of accessible tumor was done for future biomarker analysis.