Carbon dioxide is a product of the body's 'metabolism. Capnography provides an excellent picture of the respiratory process. Aim: To evaluate the effect of Teaching Program of Nurses' knowledge and practice regarding measuring End-Carbon dioxide by capnography in critical units at Assiut University Main Hospital. Design: A Quasi experimental was used. Setting: The study was carried in intensive care and major operation units at Assiut University Main Hospital. Subjects: All available nurses in Intensive care and major operation units about (60) nurses. Tools: Two tools were utilized to collect data, Tool (1): Knowledge Assessment tool, Tool (2): nurses' observational check list, Method: tow time nurses observed by the researcher before and after the teaching program, The researcher used preparatory, implementation and evaluation phases to implement study. Results: The total nurses' knowledge score improved, There was good improvement with highly significant difference related to knowledge and practice of teaching program. Conclusion: The majority of nurses had good level knowledge and practice toward measuring End-Carbon dioxide by capnography after applying teaching program. Recommendations: provide teaching and training program for nurses regarding measuring End-Carbon dioxide by capnography