Purpose: To develop guideline recommendations concerning optimal neoadjuvant therapy for breast cancer., Methods: ASCO convened an Expert Panel to conduct a systematic review of the literature on neoadjuvant therapy for breast cancer and provide recommended care options., Results: A total of 41 articles met eligibility criteria and form the evidentiary basis for the guideline recommendations., Recommendations: Patients undergoing neoadjuvant therapy should be managed by a multidisciplinary care team. Appropriate candidates for neoadjuvant therapy include patients with inflammatory breast cancer and those in whom residual disease may prompt a change in therapy. Neoadjuvant therapy can also be used to reduce the extent of local therapy or reduce delays in initiating therapy. Although tumor histology, grade, stage, and estrogen, progesterone, and human epidermal growth factor receptor 2 (HER2) expression should routinely be used to guide clinical decisions, there is insufficient evidence to support the use of other markers or genomic profiles. Patients with triple-negative breast cancer (TNBC) who have clinically node-positive and/or at least T1c disease should be offered an anthracycline- and taxane-containing regimen; those with cT1a or cT1bN0 TNBC should not routinely be offered neoadjuvant therapy. Carboplatin may be offered to patients with TNBC to increase pathologic complete response. There is currently insufficient evidence to support adding immune checkpoint inhibitors to standard chemotherapy. In patients with hormone receptor (HR)-positive (HR-positive), HER2-negative tumors, neoadjuvant chemotherapy can be used when a treatment decision can be made without surgical information. Among postmenopausal patients with HR-positive, HER2-negative disease, hormone therapy can be used to downstage disease. Patients with node-positive or high-risk node-negative, HER2-positive disease should be offered neoadjuvant therapy in combination with anti-HER2-positive therapy. Patients with T1aN0 and T1bN0, HER2-positive disease should not be routinely offered neoadjuvant therapy.Additional information is available at www.asco.org/breast-cancer-guidelines., Competing Interests: Reprint Requests: 2318 Mill Road, Suite 800, Alexandria, VA 22314; guidelines@asco.org Lisa A. CareyResearch Funding: Innocrin Pharma, Syndax, Immunomedics, Novartis, NanoString Technologies, AbbVie, Seattle GeneticsPatents, Royalties, Other Intellectual Property: Royalty-sharing agreement, investorship interest in licensed IP to startup company, Falcon Therapeutics, that is designing neural stem cell-based therapy for glioblastoma multiforme(OPTIONAL) Uncompensated Relationships: Sanofi, Novartis, G1 Therapeutics, Genentech/Roche, GlaxoSmithKline, Exact Sciences, AstraZeneca/Daiichi Sanyo, Aptitude Health(OPTIONAL) Open Payments Link: https://openpaymentsdata.cms.gov/physician/179671 Neelima DenduluriResearch Funding: Amgen, Novartis, Genentech, Lilly, Pfizer, Daiichi Sankyo, ImmunomedicsTravel, Accommodations, Expenses: Seattle Genetics Sibylle LoiblHonoraria: Chugai PharmaConsulting or Advisory Role: Pfizer, Roche, Novartis, Seattle Genetics, Celgene, Lilly, AstraZeneca/MedImmune, Bristol-Myers Squibb, Merck KGaA, AbbVie, Amgen, prime/Medscape, Daiichi Sankyo, Samsung, Puma Biotechnology, Pierre Fabre, Immunomedics, GlaxoSmithKline, EirGenix, BayerResearch Funding: AbbVie, AstraZeneca, Vifor Pharma, Amgen, Celgene, Novartis, Pfizer, Roche, Cepheid, Myriad Genetics, Immunomedics, Seattle Genetics, Daiichi Sankyo, Pierre FabrePatents, Royalties, Other Intellectual Property: Patent Pending EP14153692.0 Elizabeth A. MorrisResearch Funding: GRAIL Alejandra PerezResearch Funding: Genentech/Roche, Macrogenics, Nektar, Immunomedics, AstraZeneca Meredith M. ReganHonoraria: Bristol-Myers SquibbConsulting or Advisory Role: Ipsen, Tolmar, Bristol-Myers SquibbResearch Funding: Veridex, OncoGenex, Pfizer, Ipsen, Novartis, Merck, Ferring, Celgene, AstraZeneca, Pierre Fabre, Ipsen, Bayer, Bristol-Myers Squibb, Roche, Astellas Pharma, Medivation, Janssen, Millennium Pharamceuticals, Sanofi, Sotio, Dendreon, Pfizer, TerSeraTravel, Accommodations, Expenses: Bristol-Myers Squibb Patricia A. SpearsConsulting or Advisory Role: Pfizer Preeti K. SudheendraHonoraria: Boston ScientificConsulting or Advisory Role: Boston Scientific, Vesper Medical, Sirtex MedicalSpeakers' Bureau: Boston Scientific W. Fraser SymmansStock and Other Ownership Interests: ISIS Pharmaceuticals, Nuvera Biosciences, Delphi Diagnostics, Eiger BioPharmaceuticalsConsulting or Advisory Role: Merck, Almac DiagnosticsPatents, Royalties, Other Intellectual Property: Intellectual propertyTravel, Accommodations, Expenses: Luminex, Merck(OPTIONAL) Uncompensated Relationships: Delphi Diagnostics Rachel L. YungResearch Funding: Novartis, Odonate Therapeutics Dawn L. HershmanConsulting or Advisory Role: AIM Specialty HealthNo other potential conflicts of interest were reported.