D.Litt. et Phil. / Endometriosis is among the most common gynaecological maladies affecting women's reproductive health and is also known to be associated with infertility. The pathogenesis of endometriosis is however not well understood. Altered immunity has been indicated in the pathophysiology of this puzzling disease. Over the last decade or more the research evidence suggesting that stress might play a role in the pathogenesis of various illnesses has grown significantly. According to certain tenets of psychoneuroimmunology, behaviour and cognitive therapy, by changing an individual's reaction to stress and increasing the ability to cope with stress, thereby altering immune function, may have an effect on the proliferation of a specific illness, in the case of this study, endometriosis. Various behaviour patterns used by individuals to deal with personal and environmental stressors, have been identified. The incessant struggle to overcome real and imagined obstacles imposed by events, time and the actions of other people typifies the Type A behaviour pattern. The aims of this study were to detemine, whether there were, in a randomly chosen group of patients with endometriosis, persons with high indices of Type A behaviour; to determine whether the modification of Type A behaviour in these patients had a positive effect on their biopsychosocial functioning and finally, whether the modification of Type A behaviour had a positive effect on these patients' endometriosis-related infertility. Endometriosis patients being treated at an infertility clinic were invited to participate in the study. Forty-two subjects were recruited. A psychometric test battery was administered to all the participants. Based on the results of the Videotaped Structured Interview, the subjects were equally divided into three groups: a low index Type A group, a high index Type A group and a middle group. Experimental groups 1 and 2 received counseling aimed at reducing Type A behaviour, using the revised version of the SARCPP, which was originally used with coronary heart disease patients. The test battery was again administered after the intervention. It was found that a subset of endometriosis patients did show higher indices of Type A behaviour. Furthermore an intervention that was found to be successful in reducing the Type A behaviour intensity and frequency in subjects with coronary heart disease was also found to be similarly successful in a subset of women with endometriosis. The most significant finding was the increase in pregnancies among the group of subjects who had been exposed to the treatment. Type A behaviour modification was indeed found to be effective in the treatment of infertility in couples where the female experienced endometriosis-related infertility.