A transactional agent is a mobile agent to manipulate objects distributed on computers with some type of commitment condition. For example, a transactional agent commits only if at least one object could be successfully manipulated in the at-least-one commitment condition. Computers may stop by fault while networks are assumed to be reliable. In the client-server model, servers can be fault-tolerant according to traditional replication and checkpointing technologies. However, an application program cannot be performed if a client computer is faulty. An application program can be performed on another operational computer even if a computer is faulty in the transactional agent model. For example, a transactional agent can move to another operational computer if some destination computer where the agent to move is faulty. There are kinds of faulty computers for a transactional agent, current, destination, and sibling computers where a transactional agent now exist, will move, and has visited, respectively. We discuss how the transactinal agent can be tolerant of the types of faults. We show how a program reliably manipulating objects can be realized in a mobile agent in presence of computer faults.