Existing dialogue systems can be categorized into three main types based on their styles of questioning, namely the Finite-State, Frame-based and Free-Form strategies. Finite-State presents a list of valid options to the user in the system questions and expects the user to reply with one of the options. Slot-filling Frame-based provides a flexible approach for the system to capture any useful data that are related to the current context from the user's reply. Open-ended Free-Form is based on the questioning style used in agent-based systems, which allows the system to analyse the user's input with regard to the whole domain of the system rather than only the current context. Each of the three dialogue strategies has its own benefits in different circumstances. Therefore it is desirable to have a dialogue system that can use all three strategies in different circumstances. With such a dialogue system it is possible to use a flexible strategy such as the Frame or Free-Form in normal or optimal situations, but use the more step-by-step Finite-State strategy in situations where the system demands more control on the dialogue. The algorithm for determining the selection and transition of dialogue strategies is based on what are regarded as reasonable human behaviours. The algorithm aims to conduct conversations that are natural, efficient and able to adapt to errors of misunderstanding or misrecognition according to the dialogue history of the dialogue session and the individual user. A software application that uses the algorithm has been developed and tested for user satisfaction by a number of testers with various level of experience in using dialogue systems. Test results show that the testers had better dialogue efficiency and user satisfaction with the system that uses the multi-strategy dialogue manager and that the majority of the testers prefer to use such a system. Supplied by The British Library - 'The world's knowledge'