In the following sections, we introduce the studies of lncRNAs using models of breast cancer cells that are sensitive or resistant to drugs used for endocrine therapy (e.g., tamoxifen as the SERM, ICI182,780 as the SERD, and anastrozole as the aromatase inhibitor), models of breast cancer cells under LTED conditions, and clinical specimens of breast tumors, and intensely describe the functions and mechanisms of lncRNAs in the endocrine therapy resistance of breast cancer, as revealed by these studies. The gene discussed is CYP19A1; the disease is breast carcinoma.