Generally, studies have revealed that only a minority of people are bothered by participation in research on traumatic stress. Severity of traumatic events and subsequent responses are typically unrelated to negative reactions. We included 386 family members and caregivers (respondents) of people with intellectual and developmental disabilities (focus people). Focus people (ages 4-82) had a wide range of physical and intellectual disabilities, medical and behavioral problems, and exposure to potentially traumatic events. The measures of impact of research participation (based on J. I. Ruzek & D. F. Zatzick's [2000] Reactions to Research Participation Questionnaire [RRPQ]; S. Folkman and R. S. Lazarus's [1986, 1988] Emotional Responses to Participation Scale) showed good psychometric properties. Response to participation was highly skewed toward good understanding of informed consent, valuing participation, and minimal negative reactions. Number of traumatic events was related, positively, to only one RRPQ subscale: Valuing Participation. Implications for research and clinical work are discussed.