In modern literature the Roman law of real security is often regarded as ineffective, to which it is usually added that this did not seriously hamper the granting of credit, as in classical Rome personal security was far more important than real security. In this contribution it will be argued that this view is not correct. The sophistication of the Roman law of real security suggests that it must have played a significant role in credit transactions. Moreover, it will be argued that the Roman law of real security satisfied nearly all the requirements for an effective law of secured transactions. Its main weakness was its lack of publicity for security created over real estate and its lack of protection of bona fide third parties in respect of movable assets. It seems, however, that for a long time social norms (infamia) and transactional practices, and later criminal liability (stellionatus), provided sufficient safeguards against a malfunctioning law of real security.