ABSTRACT The complexity of mental representations of self and others is a central dimension of personality structure and interpersonal functioning. The richness, differentiation, and integration of representations develops throughout childhood and adolescence and differs among individuals and among various psychopathological populations. The nature and development of mental representations is central to object relations theories in psychoanalysis, and has been receiving empirical attention in the social cognition literature. This article reports the development of instruments for measuring the complexity of mental representations from narrative data, based on an integration of object relations and social cognition research. The present study provides preliminary support for the validity of two measures, one for use with the TAT, and the other for use with interview data such as research interviews, psychotherapy transcripts, and early memories.