This study evaluated effectiveness of group therapy for incarcerated women with histories of childhood sexual and/or physical abuse. The intervention was based on a two-stage model of trauma treatment and included Dialectical Behavior Therapy skills and writing assignments. We randomly assigned 24 participants to group treatment (13 completed) and 25 to a no-contact comparison condition (18 completed). We evaluated treatment effects, using the Beck Depression Inventory, Inventory of Interpersonal Problems, and Trauma Symptom Inventory. The data demonstrate significant reductions in PTSD, mood, and interpersonal symptoms in the treatment group.