This study aimed to investigate the psychological characteristics of chronic fatigue syndrome (CFS: Holmes et al. 1988). A battery of psychometric instruments comprising the General Health Questionnaire (GHQ), the Beck Depression Inventory (BDI), the Minnesota Multiphasic Personality Inventory (MMPI) and the Lazarus Ways of Coping (WoC) inventory, was administered to a sample of clinically-defined CFS sufferers (N = 58), to a comparison group of chronic pain (CP) patients (N = 81) and to a group of healthy controls matched for sex and age with the CFS sample (N = 104). Considerable overlap was found between CFS and CP patients at the level of both physical and psychological symptoms. This raises the possibility that CFS sufferers are a sub-population of CP patients. However, while there was some commonality between CFS and CP patients in terms of personality traits, particularly the MMPI ‘neurotic triad’ (hypochondriasis, depression and hysteria), CFS patients showed more deviant personality traits reflecting raised levels on the first MMPI factor, emotionality. Moreover, results were not consistent with the raised emotionality being a reaction to the illness, but rather were consistent with the hypothesis that emotionality is a predisposing factor for CFS. The majority of CFS patients fell within four personality types, each characterized by the two highest MMPI scale scores. One type (N = 20) reported a lack of psychological symptoms or emotional disturbance contrary to the overall trend for the CFS sample. This group conformed to the ICD-10 classification of neurasthenia.