In this paper we use institutional theory for examining how and to what extent external pressure leads to changes in the venture idea during the start-up and early life of new, knowledge-intensive ventures. From a population of 321 young, knowledge-intensive firms that underwent a training program at Linköping University, we have telephone interview data on 167. The results confirmed that the venture idea had undergone more change in ventures that had more external owners, a dominant customer, and an incubator location. Our results imply that institutional theory is a meaningful tool for understanding why and how venture ideas change over time.