The fast development of computer networks has facilitated electronic commerce. Meanwhile, some security problems may arise in such a new business environment. Nonrepudiation services, in which evidence is generated, collected, and maintained to enable dispute resolution, protect the transacting parties against any false denial that a particular event or action has taken place. In addition, fairness is a desirable requirement such that neither party can gain an advantage by quitting prematurely or otherwise misbehaving during a transaction. In this article, I investigate the techniques and protocols that use a (trusted) third party to achieve fair nonrepudiation in electronic transactions, and I discuss some applications of these fair nonrepudiation protocols.