One way to implement a fault-tolerant a service is by replicating it at sites that fail independently. One of the replication techniques is active replication where each request is executed by all the replicas. Thus, the effects of failures can be completely masked resulting in an increase of the service availability. In order to preserve consistency among replicas, replicas must exhibit a deterministic behavior, what has been traditionally achieved by restricting replicas to be singlethreaded. However, this approach cannot be applied in some setups, like transactional systems, where it is not admissible to process transactions sequentially. In this paper, we present a deterministic scheduling algorithm for multithreaded replicas in a transactional framework. To ensure replica determinism requests to replicated servers are submitted by means of reliable and totally ordered multicast. Internally, a deterministic scheduler ensures that all threads are scheduled in the same way at all re...