These findings provide empirical support for the theoretical contention that avoidance and intrusive thoughts and emotions reciprocally influence one another following stressful events. Additionally, in the months shortly after breast cancer diagnosis, intrusions and avoidance are positively related. However, the relationships attenuate over time, which could indicate resolved cognitive and emotional processing of the cancer experience. Statement of contribution What is already known on this subject? Following stressful life events, individuals often experience intrusive thoughts and feelings related to the event and they report avoidance of such reminders. Many studies demonstrate that greater intrusions predict more subsequent use of avoidance coping, and other studies show that greater use of avoidance predicts more intrusions. Their reciprocal relation has not been examined, however. What does this study add? This is the first examination of the concurrent, reciprocal influence of intrusions and avoidance. Findings suggest that accounting for the bidirectional influence of avoidance and intrusions best estimates hypothesized models. Higher intrusions and avoidance predicted each other for the first 3 months after study entry, but the relationship diminished 6 months after study entry, perhaps due to productive mental processing of the stress of breast cancer diagnosis and treatment.