Understanding LD50: A Critical Examination Rokonuzzaman 1 1 Manarat International University.   Abstract: The LD50, or Lethal Dose 50%, is a crucial metric in toxicology, representing the dose of a substance lethal to 50% of a test population within a specified time frame. This paper explores the significance, determination methods, and ethical considerations surrounding LD50. It discusses historical background, experimental procedures, and statistical analysis involved in LD50 determination, emphasizing its role in regulatory frameworks, drug development, and environmental safety assessments. Furthermore, the paper examines the limitations of LD50, including ethical concerns regarding animal testing and challenges in extrapolating results to humans. Alternative approaches to LD50 determination, such as in vitro methods and computational modeling, are also discussed, highlighting efforts to reduce reliance on animal testing. Additionally, notable examples of LD50 determination an