Through an in-depth discussion of the International Design Conference in Aspen from 1951 to 1970, this paper explores how environmental discourse underwent a shift in its connotations in the field of design during the conference. Of particular importance in this process of discursive transformation was the 1970 conference. This year's conference erupted into a conflict over the connotations of environmental discourse as environmental discourse outside of design impacted on and transformed the environmental discourse within design. This article examines the different concepts of the term 'environment', as presented by speakers and participants at the International Design Conferences in Aspen from 1951 to 1970, and especially focuses on the debates surrounding 'environment' at the 1970 conference. The article concludes by exploring the implications of this event and summarises the role of the 1970 International Design Conference in Aspen at this crucial turning point in environmental discourse. The aim is to explain and strengthen the significance of discourse a design conferences in the history of design, and to explore a new direction of design history research.