Recommender systems promise to support travelers in complex decision-making processes; however, whether a recommendation is seen as credible advice and actually taken into account not only depends on travelers' perceptions of the recommendation but also of the system as the advice giver. A scale to measure recommender system credibility was developed and tested. The results confirm that credibility has two dimensions: expertise and trustworthiness. Further, significant gender differences in credibility perceptions were found. The findings also indicate that respondents prefer humans as recommendation sources and that this preference is influenced by perceptions of lack of credibility of recommender systems as well as gender-specific preferences. Implications for future research and for recommender system design are discussed.