This paper explores how entrepreneurs engage in prototyping as part of the venture development process. We conduct a qualitative field study of 156 instances of prototyping across eight venture development processes. From a theoretical perspective, we build on alternative and complementary views of entrepreneurial action and their implicit modes of prototyping, emphasizing experimentation and transformation. Our findings identify three important themes in the prototyping process. These include purposes where the entrepreneurs use prototyping for either flexible experimentation or directed transformation. Further, the entrepreneurs predominantly engage in prototype recycling and skills bricolage when prototyping. Accordingly, the studied entrepreneurs carefully navigate purpose and resource investments in prototyping, making extensive use of their existing resource base of skills and prototypes. After noting the positive aspects of prototyping, we also discuss the potentially destructive outcomes of misapplied prototyping in the form of prototyping myopia and problematic path dependencies of the different ways of prototyping.