Most User Interface Management systems are state based and some use state transition diagrams for dialog specification. Although these diagrams have significant advantages, they suffer from drawbacks that make them impractical for the specification of complex user interfaces. Statecharts are a hierarchical extension of state transition diagrams and are well suited for specification of complex user interface dialogs. Statemaster is a UIMS implemented in C + + that uses statecharts for dialog specification. It has been successfully used both for rapid prototyping and target implementation of user interfaces. This paper describes the use of statecharts for dialog specification and the implementation of Statemaster.