Ph.D. / Chronic Fatigue Syndrome (CFS) is a disabling and poorly understood multisystem illness. The illness is characterised by the principal symptom of persistent or intermittent unexplained fatigue, and has physical, psychological, social and community implications. Since CFS remains unexplained by a conventional biomedical diagnosis, confusion and controversy surround the illness. The confusing and controversial issues are the diagnosis, etiology, psychiatric states and the role of psychosocial factors. The overall aim of this study was to investigate the role of certain psychosocial factors, namely personality preferences or type, coping resources, locus of control and Type A behaviour pattern (TABP), in CFS. The total sample consisted of 70 subjects from four samples, namely the CFS patient sample (n = 21), coronary heart disease (CHD) patient sample (n = 14), depression patient sample (n = 15) and healthy sample (n = 20). The CHD patient, depression patient and healthy samples were included for comparative value. The broad hypothesis was that specific personality preferences or types as well as specific coping resources, locus of control and TABP would be characteristic of the CFS patient sample. The second hypothesis was that the CFS patient sample would significantly differ from the comparative samples on these psychosocial factors. Finally, it was hypothesised that the psychosocial factors would be correlated and hence have predictive value for the development and maintenance of CFS. On the Myers-Briggs Type Indicator' s (MBTI®), the CFS patient sample was found to have an over-representation of the introversion (61.9 %), intuition (52.4 %), feeling (66.7 %) and judging (76.2 %) preferences. An analysis of the type distribution and frequencies resulted in two whole types, namely ISFJ and INFJ. A normative interpretation of the Coping Resources Inventory° (CRI©) profile revealed that the CFS patient sample's coping resources in the various domains of cognitive, social, emotional, spiritual/philosophical, physical and total resources were below the mean. The results of the Locus of Control (LOC) Questionnaire revealed that the CFS patient sample primarily utilises an internal locus of control. However, the sample was also found to have a low state of self-regulation. In comparison to the healthy sample, the CFS patient sample had a significantly higher external locus of control. These findings lead to the hypothesis that during stressful situations (such as illness), the CFS patient sample's low state of self-regulation may result in them utilising an external locus of control. The CFS patient sample was found to have a higher mean TABP score than the mean TABP score of the total sample. This sample was also found to have a significantly higher mean TABP score than the healthy sample. Hence, it was concluded that the CFS patient sample exhibited a TABP. The Mann-Whitney U tests were utilised to determine the differences between the CFS patient sample and the various comparative samples. Various of the assessed psychosocial factors were found to differ significantly. However, most of the differences were found between the coping resources of the various samples. Correlations were drawn between the various assessed dimensions to determine whether the psychosocial factors have predictive value. On the MBTI®, a preference for sensing was associated with an external locus of control whereas a preference for judging was associated with a high TABP. A high TABP was associated with a high external locus of control. An external locus of control and TABP have been identified in previous studies on chronic illnesses as predisposing and maintenance factors. Hence, it was hypothesised that a preference for sensing and for judging respectively may be personality preferences that play a role in the development and maintenance of CFS. Subsequently, a high external locus of control and a high TABP respectively were also hypothesised to be predisposing and maintenance factors. The findings of the correlations also lead to the hypothesis that CFS patients with an extraversion and a thinking preference respectively have the ability to cope more effectively with their illness and may even recover quicker. Chronic Fatigue Syndrome patients with a high internal locus of control and a high state of self-regulation were also hypothesised to have a better overall ability to cope with their illness and may hence recover quicker. The final conclusion of the study's findings was that personality preferences and type, coping resources, locus of control and TABP interact within a complex matrix of socio-behavioural and biological factors in the development and maintenance of CFS. The value of the study is the identification of individuals at risk for the development of CFS and the psychosocial factors involved in the development and maintenance of CFS. In addition to this value, the MBTI ® results can be used to alert psychologists to the issues frequently associated with each MBTI® preference and can hence assist psychologists in the psychotherapeutic treatment of CFS patients. The results of the coping resources' deficits can also assist psychologists in the design and development of stress management programmes for CFS patients.