The products of engineering design are everywhere, but who or what determines their form and function? Their surfaces are usually cold, seemingly objective, as if they existed outside of history of the technologies that are so much a part of our lives. Written by a practising engineer, "Designing Engineers" yields clues to this mystery by probing deeply into the everyday world of engineering. In doing so, it reveals significant discrepancies between our ideal image of design as an instrumental process and the reality of design as a historically-situated social process that is full of uncertainty and ambiguity. This text describes the evolution of three disparate projects: an x-ray inspection system for airports, a photoprint machine, and a residential photovoltaic energy system. In each case, we are taken through the hallways and into the meeting rooms of the company to watch over the shoulders of engineers as they engage in the manifold individual and collective work that goes into designing a new product. Louis Bucciarelli was a consultant to one project and participated in the design process for the other two. In all three projects he examines both object - the way participants understood how things work - and process - the way they go about designing. What he learns is that engineering design is a social process that involves constant negotiation among many parties, not just engineers but marketing people, research scientists, accountants, and customers as well.