The MHQ is a brief self-rating inventory purporting to measure aspects of six distinct categories of psychoneurosis and affective status. It has been found to be a reliable instrument and also valid as a profile measure. Two individual scales have also previously been explored in respect of validity. The present report describes a further attempt to examine the validity of individual scales in relation to pertinent single clinical diagnostic entities in a study involving 800 patients. The phobic and obsessional scales are found to be particularly accurate and differentiating in this respect. Patients variously diagnosed as suffering from anxiety states, depressive states and personality disorder tend to score very highly on several scales. The instrument serves overall to distinguish satisfactorily between such populations and others suffering from schizophrenia and anorexia nervosa. It also markedly differentiates them from ‘normal’ populations.