Consumers' concerns about privacy, security, and control of personal information highlight the importance of trust in building marketing relationships in the computer-mediated environment. Internet firms have begun posting third-party certifications, labelled “trustmarks”, as signals of reliability, credibility, and general trustworthiness. This paper integrates the literatures on signalling theory and trust, and makes extensions to the internet. It identifies and categorises sets of internet signals, highlighting the critical role of trustmarks in the computer-mediated environment. It develops a series of propositions related to the effectiveness of trustmarks, including variables such as source and culture. Lastly, it provides direction for future research.