The Hill Interaction Matrix (HIM-G) was used to measure specific behavioral characteristics of the subjects in interaction with selected therapeutic factors. Two basic dimensions were measured. The content-style dimension described four therapeutic levels of group discussion: topic, group, personal, and relationship. The second dimension, work style, described qualitative levels of work occurring during the therapy: conventional, assertive, speculative, and confrontation. The percentage of time the group spent in each cell of the matrix and percentile norms comparing obtained percentages to norm groups were calculated. Three of the four high therapeutic categories in which this group concentrated its efforts were significant in therapeutic value related to specific drug-addicted behavioral characteristics. These characteristics include social isolation, impaired judgment and social functioning, impulsiveness, mood lability, aggressiveness, acting-out traits, rebelliousness, and difficulty with anger. The three therapeutic categories were personal-confrontive, relationship-speculative, and relationship-confrontive. These results confirmed the treatment value of the marathon group format. 1 figure, 2 tables, and 21 references