Institutional theory is employed 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 Linkping University, Sweden, structured telephone interview data were obtained from 167 firms. 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. The results imply that institutional theory is a meaningful tool for understanding why and how venture ideas change over time.