Recent work by Jim Herbsleb at Carnegie Mellon University found that volunteer contributions to open source software development projects increased in the aftermath of “community code engagement” (CCE) events like hackathons or summer coding projects. Yet little is known about how exactly CCEs lead to more contributions from volunteers, what makes for a good CCE, and what pitfalls to avoid. This grant funds efforts by Jim Herbsleb to continue his examination of how CCEs spur contributions to scientific software development and to compile a list of best practices for CCE design and implementation. Over the next three years, Herbsleb and his team will study successful and failed CCEs through participant observation, semistructured interviews, and quantitative analysis of software version histories to determine contribution patterns. He will then develop a set of best practices for CCE design and test these guidelines in a series of pilot projects.  Herbsleb and his team will then develop a CCE Toolkit that they will introduce to scientific software developers at a series of workshops attached to disciplinary meetings. The project promises to provide useful new information on how to spur engagement in community software development, an activity that is likely to become increasingly important as science moves further and further into the information age.