The use of tangible objects is paramount in industrial design. Throughout the design process physical prototypes are used to enable exploration, simulation, communication, and specification of designs. Although much is known about prototyping skills and technologies, the reasons why and how such models are employed in design practice are poorly understood. Advanced techniques and design media such as virtual and augmented prototyping are being introduced without insight as to their benefits. We believe that an augmented prototyping system, that is, employing augmented reality technology to combine physical and digital representations, could positively influence the design process. However, we lack knowledge on why and how it might facilitate design. This paper reports on case studies performed in different domains of industrial design. At each of three Dutch design offices, a project was followed with particular attention to physical prototyping and group activities. The projects encompassed information appliance design, automotive design, and interior design. Although the studies vary in many aspects (product domain, stakeholders, duration), the findings can be applied in conceptualizing advanced prototyping systems to support industrial design. Furthermore, the data reveal that the roles of a prototype in current practice are not necessarily utilitarian; for example, the prototype may serve as a conversation piece or as seducer. Based on so-called “hints,” bottlenecks and best practices concerning concept articulation are linked to usage scenarios for augmented tangible prototyping. The results point to modeling and communication scenarios. Detailed study of the cases indicates that communication activities, especially design reviews, would benefit most from interactive augmented prototyping.