In the application domain of online information services such as online census information, health records and real-time stock quotes, there are at least two fundamental challenges: the protection of users? privacy and the assurance of service availability. We present a fault-tolerant scheme for private information retrieval (FT-PIR) that protects users? privacy and ensure service provision in the presence of malicious server failures. An error detection algorithm is introduced into this scheme to detect the corrupted results from servers. The analytical and experimental results show that the FT-PIR scheme can tolerate malicious server failures effectively and prevent any information of users from being leaked to attackers. This new scheme does not rely on any unproven cryptographic premise and the availability of tamper-proof hardware. An implementation of the FT-PIR scheme on a distributed database system suggests just a modest level of performance overhead.