The awareness about the gap between general design theory and design practice is increasing. Design practice is not really served with the results of current design theory. To build a bridge between theory and practice, design researchers should know what is really going on in practice. To explore design practice and to find the most important characteristics of design situations, I have chosen an empirical approach based on case studies in which design projects in different disciplines are compared. In each case study, an individual designer is interviewed and the design documents are analysed. The results in this article are based on two architectural projects, two software-engineering projects and two mechanical-engineering projects. The cross-case analysis has resulted indescriptions of design situations in these disciplines. A preliminary design frame to describe design situations in different disciplines has been derived. Based on similarities and differences in the descriptions, conclusions concerning design theory, design education and design practice are given. The most important conclusions are the following. First, designers are often not aware of their design process, but focus mainly on the product. Second, software designers more often than architects and mechanical engineers use methods to structure their overall design process.