This virtual course is designed in a two-day format to provide an introduction to the use of flow cytometry for identification of minimal/measurable residual disease (MRD) in B Lymphoblastic Leukemia/Lymphoma (B-LL). The intended audience of this course includes those performing this testing and those who are considering bringing on this testing in their laboratory settings. This course may be appropriate for students, technologists, pathologists, and flow cytometry laboratory directors or supervisors. Some familiarity with interpretation of flow cytometric data is suggested for participants in day two.