Although a support person is required by many centers during the predictive testing protocol for Huntington disease (HD), little is known about the psychosocial impact of predictive testing on persons serving in this role. Eighteen adults who were support persons during predictive HD testing in one HD testing center completed a semi-structured interview to describe their experiences. Participants also completed the Impact of Events Scale (IES) to assess perceptions of emotional distress regarding predictive testing and the State Anxiety Scale of the State Trait Anxiety Inventory (STAI) to assess anxiety regarding the interview. State anxiety scores were similar to normative values for working adults. Although support persons for individuals with a positive gene test scored higher on all measures of the IES than those who were support persons for persons with negative gene mutation results, these differences were not statistically significant. Support persons identified aspects of the protocol that did not fit their needs, perceived the testing process as extending into subsequent caregiving responsibilities when the test was positive, and were uninformed regarding specific caregiving issues for family members with the gene mutation. The impact of the testing experience appeared to be most intense for those support persons who were at-risk offspring of probands. Findings suggest that individual assessment of support person needs may allow more focused counseling of support persons during predictive genetic HD testing. Collaboration with health care providers may facilitate symptom manage-ment following testing. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:353-359, 2000.