Gender differences, also called gender bias, are known to influence research findings in multiple fields. Given that only a limited amount of information is available on gender differences in symptoms in oncology patients, the purposes of this study, in a sample of outpatients receiving chemotherapy (CTX, n = 926), were to evaluate for gender differences in demographic and clinical characteristics, as well as in occurrence rates for and severity ratings of fatigue, energy, and sleep disturbance. Patients completed self-report instruments and medical records were reviewed for disease and treatment information. Across these three common symptoms, female patients had higher occurrence rates for clinically meaningful levels of fatigue and sleep disturbance, as well as decrements in morning energy. In addition, females reported higher severity scores for morning and evening fatigue, sleep disturbance, and decrements in evening energy. Both genders had significant problems with sleep maintenance. All three symptoms were common in both genders. The three symptoms appear to be distinct, yet related and should be assessed on an ongoing basis during CTX.