This systematic review examines the causes, effects, and solutions of emergency department (ED) crowding, a critical issue affecting healthcare quality and access. The review, conducted by Nathan R. Hoot and Dominik Aronsky, involved a comprehensive PubMed search to identify articles that studied these aspects of ED crowding. Two independent reviewers identified 93 articles meeting the inclusion criteria, with 33 articles focusing on causes, 27 on effects, and 40 on solutions. Common causes included non-urgent visits, frequent-flyer patients, influenza season, inadequate staffing, inpatient boarding, and hospital bed shortages. Effects were categorized into adverse outcomes (e.g., patient mortality), reduced quality (e.g., transport and treatment delays), impaired access (e.g., ambulance diversion, patient elopement), and provider losses (e.g., financial impact). Solutions included additional personnel, observation units, hospital bed access, non-urgent referrals, ambulance diversion, destination control, crowding measures, and queuing theory. The review highlights the complex nature of ED crowding and suggests that further high-quality studies are needed to better understand and address this issue.This systematic review examines the causes, effects, and solutions of emergency department (ED) crowding, a critical issue affecting healthcare quality and access. The review, conducted by Nathan R. Hoot and Dominik Aronsky, involved a comprehensive PubMed search to identify articles that studied these aspects of ED crowding. Two independent reviewers identified 93 articles meeting the inclusion criteria, with 33 articles focusing on causes, 27 on effects, and 40 on solutions. Common causes included non-urgent visits, frequent-flyer patients, influenza season, inadequate staffing, inpatient boarding, and hospital bed shortages. Effects were categorized into adverse outcomes (e.g., patient mortality), reduced quality (e.g., transport and treatment delays), impaired access (e.g., ambulance diversion, patient elopement), and provider losses (e.g., financial impact). Solutions included additional personnel, observation units, hospital bed access, non-urgent referrals, ambulance diversion, destination control, crowding measures, and queuing theory. The review highlights the complex nature of ED crowding and suggests that further high-quality studies are needed to better understand and address this issue.