Objective: To examine whether (a) Living in the Face of Trauma (LIFT), a group intervention to address coping with HIV and childhood sexual abuse (CSA), significantly reduced traumatic stress over a 1-year follow-up period more than an attention-matched support group comparison intervention; and (b) reductions in avoidant coping over time mediated reductions in traumatic stress. Method: In a randomized controlled trial, 247 participants completed measures of traumatic stress and avoidant coping at pre- and post intervention, and at 4-, 8-, and 12-month follow-ups. Latent growth curve modeling examined changes over the 5 time points; standardized path coefficients provide estimates of effects. Results: As compared with the support intervention, the coping intervention led to a reduction in traumatic stress over time (b = -0.20, p less than 0.02). Participants in the coping intervention also reduced their use of avoidant coping strategies more than did participants in the support intervention (b = -0.22, p less than 0.05). Mediation analyses showed reductions in avoidant coping related to reductions in traumatic stress (b = 1.45, p less than 0.001), and the direct effect of the intervention on traumatic stress was no longer significant (b = 0.04, ns), suggesting that changes in avoidant coping completely mediated intervention effects on traumatic stress. Conclusions: The LIFT intervention significantly reduced traumatic stress over time, and changes in avoidant coping strategies mediated this effect, suggesting a focus on current stressors and coping skills improvement are important components in addressing traumatic stress for adults living with HIV and CSA. (Contains 2 figures and 1 table.)