BACKGROUND: Interventions intended to motivate donors to return can be costly and time consuming. The current study examined the effect of a Web-based automated interview, informed by motivational interviewing and self-determination theory, on donor intention, motivation, and behavior in a sample of highly experienced donors. STUDY DESIGN AND METHODS: Approximately 1 week after donating, 1177 highly experienced whole blood donors (mean prior donations, 35.5; mean age, 46.9 years; 66.3% female) participated in a study in which they were randomly assigned to either a donor motivational interview (n = 544) or knowledge interview (n = 633). Measures of donor motivation and psychological need support were obtained before the interviews, and again at postinterview assessments conducted approximately 2 days later and 7 weeks later. Blood center records were used to assess repeat donation attempts for 1 year after the interviews. RESULTS: Relative to the knowledge interview, participants in the motivational interview had larger increases in donation intention and self-efficacy from preinterview to the first follow-up. Among women only, the motivational interview was associated with greater competence and relatedness increases at both follow-up assessments. CONCLUSION: An automated motivational interview appears to be a feasible way to promote donation intention and self-efficacy. Although the observed effects were small among highly experienced donors, we are currently assessing the potential effect of this intervention among less experienced donors.