This paper discusses a method and supporting CASE tool for the production of formal specifications in Z  on the basis of an object-oriented analysis model. The analyst describes the required objects using diagrams and structured text and specifies formally the responses to events at the level of the individual object instances. The tool then generates the Z specification. The user of the tool need not in general be concerned with much of the structure and specific syntax of Z itself. The structure and components of the analysis models and the related Z are closely matched to aid understanding and support traceability. The tool enables the user to navigate between related components within and between both the analysis models and the generated Z specification. The paper describes the components of the models and the style of Z which is generated.