International Journal of Group Psychotherapy 61(3): 366-395 Abstract Evidence-based psychotherapy is typically based on treatment outcome for the average patient in aggregate designs; reports on individual non-responders are rarely published. In this observational study, we explored factors that might have contributed to non-response in long-term dynamic group psychotherapy. Eight patients (14%) who did not change were compared with 48 treatment responders on clinical variables, and their case stories were retrospectively scrutinized for explanatory factors. The non-responders had less initial distress, stayed for shorter durations in therapy, and were more dissatisfied with their group and therapists. Based on detailed case stories, attempts are made to tease out idiographic hypotheses why each patient did not change during group analysis.