While cohesive devices do not in themselves, or in their aggregate, correspond to the degree of coherence in a text, the measure of ‘cohesive harmony’ developed by Hasan (1984) does constitute an index of the ‘textness’ of extended discourse, including interactive exchanges. A team of functional linguists and psychiatrists investigated the discourse correlates of techniques in the Conversational Model of Psychotherapy (following Meares, 1993, 2005). As one dimension of this investigation, the ‘frag- mented’ discourse of dissociating patients was analysed for cohesive harmony. This analysis provided a basis for discriminating degrees of fragmentation in the discourse of patients interacting with therapists, and results help explain the paradoxical combi- nation of disaggregation and fusion in the way such patients construe their experience. Additionally, the method provides new forms of evidence of coherence and consensus between therapist and patient, indices of progress which might otherwise be ‘lost’ or argued on an intuitive basis alone.