Despite the growing importance of the Internet as an information and purchase channel for the tourism industry, there is still a gap in the literature about the motivations and barriers involved in the online consumption of tourism related services and products. The central hypothesis of this study is that trust and its antecedents have an important role in the formation of the intention of purchasing travel products and services on the Internet. Based on a literature review, several relevant antecedents to online trust and tourism purchase behavior were identified. A structural model was then proposed to test sixteen hypotheses relating the selected constructs to purchase intent. Data from a survey of 292 previous buyers of online tourism products and services was used to test the proposed model. The results confirm most of the hypotheses, with significant relationships being found between trust and the other addressed constructs, most of which were found to significantly influence the intention to purchase tourism-related services or products online.