Chronic Fatigue Syndrome is a perplexing disease potentially affecting
thousands of Americans. Several behavioral rating scales have been de
veloped to assess this condition; however, few capture the patterns of
energy fluctuations that occur with this syndrome. Data are presented
that suggest that fatigue needs to be measured over time and in refer
ence to amount of activity and mood. Measurements that focus on only o
ne time point might not accurately assess fatigue, which is the most s
alient symptom of this condition.