This paper examines the stigmergic dimensions of online interactive creativity through the lens of Picbreeder. Picbreeder is a web-based system for collaborative interactive evolution of images. The Picbreeder applet starts by randomly generating several images, which are then mated and mutated based on the user’s selections. The user can then publish the image to the Picbreeder website where other users can download and continue the image’s evolution. Within this process, users collaboratively create imageswith significant complexity, all without explicit communication. In short, Picbreeder encourages a new form of stigmergic collaborative creation. The most surprising result of the Picbreeder experiment during more than 3 years of operation has been the quality of the resulting images, despite the limited ways of interacting with other users. This fact challenges some commonly held notions of creativity, both online and offline. While current cognitive research in creativity places significant emphasis of the personal traits and cognitive structures that give rise to creative thought, Picbreeder highlights the potential for the emergence of creativity through stigmergic interaction. Picbreeder offers a rich data set for analysis of collaborative interaction with over 155,000 inputs from hundreds of users combined to create over 7500 images. It is hoped that the insights offered in this paper will influence both the understanding of collaborative creativity and the development of new modes of online creative interaction.