Developers of User Interface Management Systems (UIMS) have demonstrated that separating the application from its user interface supports device independence and customization. Interfaces produced in UIMS are typically crafted by designers expert in human factors and graphic arts. Little attention has been paid, however, to capturing the knowledge of such experts so that interfaces might be automatically generated by the application of style rules to additional applications. This paper considers how toolkits and style rules can be structured so that the resulting interfaces take advantage of the best human factors and graphic arts knowledge, and are consistently styled. © 1989 ACM.