Children with cancer often receive treatment that may include both chemotherapy and radiation. These agents primarily can affect the body's hematopoietic system. The authors designed a teaching poster, in both English and Spanish, to assist in teaching the key concepts of low blood cell counts to pediatric patients and their families. Having a child with cancer often is an overwhelming experience, and most parents and family members need to learn new information in a variety of ways to maximize their understanding and retention. This poster was not designed to be a substitute for patient-family teaching but, rather, to serve as a reinforcement tool.