<h4>Purpose</h4>We aimed to evaluate for associations between HIV status, psychosocial factors, and adjuvant endocrine therapy (AET) adherence in South African (SA) women with estrogen receptor positive (ER+) breast cancer (BC).<h4>Methods</h4>We enrolled South African women with early-stage ER + BC in remission and prescribed tamoxifen or an aromatase inhibitor to the prospective observational study. This evidence concerns the gene ESR1 and breast cancer.