Background Bone marrow transplantation is an advanced therapeutic intervention that is required for a number of malignant and nonmalignant medical conditions, often for critically ill patients. the nurses needed to be provided with knowledge and practice to give high quality of care for patient. Aim of the study: was to evaluate The effect of teaching program on nurses`performance regarding bone marrow transplantation. Study Design: Quasi-experimental pre-post test research design was utilized.. Setting The study was conducted in bone marrow transplantation unit and other critical care unit at south Egypt cancer institute at Assiut University hospital Sample: All nurses (30) from above mentioned setting. Tools: An interview questionnaire for the nurse, Tool 1 knowledge assessment tool will be utilized, Tool 2. Observational chicklist for practise assessment tool will be utilized Results nurses knowledge was significant improved from 18.47﴾to﴿32.77 respectively and nurses practice was improved from 48.47 to96.5 after the implementation of the program. Conclusion: There were highly significant improvement in knowledge and practice after implementation of program about bone marrow transplantation. Recommendation; Continues nursing education and training programs at critical care units should be organized within south Egypt cancer institute