Surrogate (proxy) decision makers must make research decisions for people with dementia who lack decision-making capacity. Proxies’ decision-making processes are minimally understood. We randomly assigned 82 proxies of AD patients to informed consent for one of three hypothetical protocols with differing levels of risk and benefit. Proxies answered questions about potential benefits of the described research to the patient and society, as well as about whether they would enroll their relative and why or why not. Proxies interested in enrolling their relative cited the potential for direct benefit to their relative, altruism, and trust in researchers. Those declining cited risks, inconvenience, and stage of illness. Proxies weighed numerous factors, incorporating both substituted judgment and best interests standards in their decision-making processes. Although further empirical work is needed to understand the influences on and adequacy of proxies’ decision making regarding research, these findings can help inform policy regarding surrogate consent.