Participants with chronic fatigue syndrome were categorized into subtypes based on actigraphy and illness selfreport symptom severity data. Each method identified two groups of patients, one with severe and one with less severe manifestations of the illness. For both subtypes, those in the more severe category had more physical functioning problems than those in the less severe categories. However, for the illness self-report symptom group, those in the more severe category had significantly more impairment in sleep, anxiety, depression, and pain, and more concurrent psychiatric status and Fibromyalgia than those in the less severe category. In contrast, those in the more severe actigraphy subtype group in comparison to the less severe group had more impairment in quality of life and cortisol readings. These findings suggest that CFS subtypes based on symptom severity and amount of activity identify different groups of patients with varying types of impairments.