Although substantial research has been conducted on chronic fatigue syndrome (CFS) over the past decade, the syndrome remains poorly understood. The most recent case definition describes CFS as being characterized both by disabling fatigue and by subjective reports of difficulty with concentration and "short-term" memory. However, research into the neurocognitive and psychological functioning of individuals with CFS has provided mixed objective results. The current paper reviews studies that have examined the neurocognitive and/or psychological functioning of individuals with CFS. Changes in research design and instruments employed to study individuals with CFS are suggested.