Fatigue is a prevalent and distressing symptom for adolescents during cancer treatment. Adolescents complain that fatigue is affected by sleep-wake disturbances, but little is known about the association between these symptoms and how they vary over time in adolescent patients. Aims of this study, based on a developmental science framework, were to describe patterns of fatigue and sleep-wake disturbances of adolescents during one month of chemotherapy. Associations between fatigue, sleep- wake disturbances, and quality of life were also explored. The study used mixed methods of self-report to collect data from 20 adolescents with a variety of cancer diagnoses. The adolescents described their daily fatigue using rating scales and qualitative diaries. Multidimensional fatigue and quality of life were measured weekly with modules from the PedsQLTM Measurement Model, and sleep-wake disturbances were measured with the General Sleep Disturbance Scale. Data analysis was conducted using visual graphic analysis techniques and nonparametric statistics. For adolescents who received chemotherapy every 3 to 4 weeks, the most common fatigue trajectory was an increase in fatigue severity 1 to 3 days after chemotherapy, followed by a declining 'roller-coaster' trend that continued until their next treatment. Adolescents who received weekly chemotherapy showed more frequent peaks and troughs in fatigue severity that did not diminish across one month. These adolescents complained of frequent daytime sleepiness and poor sleep quality. Increased symptom severity and decreased quality of life occurred