This study measured circadian activity rhythms (CAR) and fatigue in children and adolescents with acute lymphoblastic leukemia on maintenance chemotherapy during the 5 days prior to a pulse of dexamethasone and the 5 days after the start of dexamethasone. CAR was measured via an actigraph worn continuously for 10 days. Fatigue was measured at 4 time points. The fatigue measures used for this study were Fatigue Scale-Child, Fatigue Scale-Adolescent and Fatigue Scale-Parent. The aims of this descriptive study were to compare CAR during the periods before and during dexamethasone therapy, and to explore the hypothesis that less robust CAR was associated with greater fatigue.