This paper reports a multi-national, multi-institutional study to investigate Computer Science students' understanding of software design and software design criteria. Students were recruited at two levels: those termed 'first competency' programmers, and those completing their Bachelor degrees. The study, including participants from 21 institutions over the academic year 2003/4, aimed to examine students' ability to generate software designs, to elicit students' understanding and valuation of key design activities, and to examine whether students at different stages in their undergraduate education display different understanding of software design. Differences were found in participants' recognition of ambiguity in requirements; in their use of formal(and semi-formal) design representation and in their prioritisation of design criteria.