This study is for male and female children, adolescents, and young adults under the age of 25 who have been diagnosed with Chronic Myeloid Leukemia (CML) that is in the earliest phase known as the chronic phase. Chronic phase means that the level of disease is very low and is often called molecular remission.  To keep the CML at this low level, people typically take a type of drug called a tyrosine kinase inhibitor (TKI), such as imatinib, dasatinib, and nilotinib every day.
   
Participants in this study will be asked to stop taking their TKI medication. They will have clinic visits and disease status will be monitored every 4 weeks during the first year, every 6 weeks during the second year and then every 12 weeks during year three.

If at any point during the study the CML comes back (loss of molecular remission), participants will restart the TKI medication. After restarting the TKI medication, participants will have clinic visits and disease status will be monitored every 4 weeks during the first year, every 6 weeks during the second year and then every 12 weeks during year three.  

All participants will be asked to complete some short tests on the computer about their attention and memory which will take about 20 - 30 minutes and parents/guardians of those under 18 will be asked to fill out paper questionnaires about participants everyday thinking and learning functions which will take about 10 - 15 minutes. If a participant is 18 years or older, they will complete the paper questionnaire.