In this paper I argue that in Western contemporary societies testimony is structured by norms of reciprocation and thus is best understood as involving the exchange of gifts rather than, as philosophers and game theorists have tended to presume, market transactions. My argument is based on an initial analysis of the reactive attitudes that are exhibited in testimonial exchanges. I highlight the central role played by the reciprocating attitudes of gratitude and gratification respectively in the recipient and the donor of testimony. This analysis leads to an account of the speech act of telling that is the primary vehicle of testimony. Telling, I argue, is a commissive but it is not, as it is usually presumed, akin to promising. Instead, its nature is that of an offer of a gift. Finally, I develop an account of the norms of trust and trustfulness as reciprocating social norms. I show that adopting these norms provides a particularly effective solution of the problem of cooperation. The solution is particularly effective because it incentivises both the sharing of epistemic goods and the acquisition of further such goods so that one is able to share them.