[en] Ergonomic criteria are receiving increasing attention from designers but their applications do not ensure that technology matches the user's abilities, needs, and work constraints. In this paper, we used two series of studies conducted in the healthcare system to illustrate how important work analysis is in evaluating new technology in order to identify critical dimensions of work and anticipate the impact of the devices on these dimensions: one looking at a new automatic drug device for anesthetists and one at a new robotic surgery system. Given the results, we developed a methodology for evaluation of new technology in complex systems. The aim is to insist to assess the impacts of technology on all the dimensions of work: technical, performance, cognitive, organizational, and economic. Which dimensions and criteria will be developed more in detail depends on the results of the work analysis.