It is common clinical knowledge that parents of schizophrenic patients show an apparent disability to comprehend their children's illness. They often minimize its severity or show complete lack of insight and deny gross psycho-pathological symptoms. The concept of illness by parents of schizophrenic patients is the subject of the present investigation. Investigations of such attitudes are not common in the literature. They are impeded by the lack of appropriate objective techniques of measurement. The Repertory Grid method (Kelly, 1955) provides a flexible and sensitive instrument for investigation of single subjects. According to Kelly's theory, each person has his own unique way of construing. He evaluates a set of elements within his range of comprehension, using Personal Constructs in a network of interrelationships. Difficulties occur, however, when groups of people are to be compared. One can compare groups by the way they use Constructs to evaluate a set of Elements; but one must ensure not only that the Elements are within the range of convenience of all subjects of the group but also that Constructs used by the group occupy some significant place in the construct system of each person of the group. The work reported in this paper was performed in two distinct phases.