This article reports the development of a marker-based method for rating assimilation in psychotherapy with a case study of a woman, Sarah, who was treated for depression with process-experiential psychotherapy. To increase the rigor of the qualitative case study methodology, independent judges rated passages--taken out of context and randomly ordered--from the qualitative analysis. The authors examined levels of training required to make quantitative judgments by comparing ratings from 4 graduate students and 4 undergraduate students. Pooled reliabilities of the 2 groups of raters were high (0.90 and 0.84), and the estimated reliability of single graduate student raters was acceptable (0.70). Consistent findings across a series of related case studies are reviewed to address the generalizability of the findings.