A dissertation submitted to the Faculty of Arts in partial fulfilment of the requirements for the Degree of Master of Arts (Clinical Psychology) in the Department of Psychology at the University of Zululand, South Africa, 2015 / This is a case study for the three categories of psychology: clinical, counselling and educational, and focuses on evaluating the diagnostic interview styles that clinical, counselling and educational psychologists employ when seeing their patients/clients.I t also aims to check consistency in the diagnostic interviewing styles they employ to formulate diagnoses and treatment plans for their patients/clients. The study indicates that psychologists undergo similar training and are regulated by the same professional board (HPCSA), though their scope of practice is not the same. However, the clinical/diagnostic interview is common among all psychologists. If they employ a diagnostic interviewing style that is not appropriate to the client’s/patient’s needs and problems, accurate diagnosis will not be achieved, and proper treatment or intervention will not be possible. This study is unique because it evaluates psychologists’ interviewing styles.