Concepts from the health belief, transtheoretical, and dual process models were used to examine how siblings of individuals diagnosed with colorectal cancer (CRC) before age 56 made decisions about CRC screening. Siblings (N = 504) were assessed for CRC screening practices and intentions, pros, cons, processes-of-change, perceived risk of CRC, perceived severity of CRC, preventability of CRC, cancer-related distress, and sibling relationship closeness. Physician and family recommendation and knowledge were also assessed. Fifty-seven percent of participants (n = 287) were compliant with CRC screening. Logistic regression indicated that perceived pros and cons, perceived risk, commitment to screening, health care avoidance, and sibling closeness were associated with screening compliance. Physician and family recommendation were also strong correlates. A similar set of factors was associated with stage of adoption of CRC screening.