The studies here reported are concerned with the application of some of the techniques of measurement to problems of mental health. They constitute the preliminary steps in a programme of research that envisages: (i) the possibility of assisting mental diagnosis by means of objective experimentation, the purpose of which is to isolate variables in personality that are significant in their relationships to degrees of mental stability; (ii) the functional interpretation of these variables; (iii) the employment of any quantitative criteria that can be thus established, in demonstrating the influence of therapeutic and positive mental hygiene programmes.