We are providing a preview of a project that analyzes two field experiments with 1,974 software developers at Microsoft and Accenture to evaluate the productivity impact of Generative AI. As part of our study, a random subset of developers was given access to GitHub Copilot, an AI-based coding assistant that intelligently suggests ‘completions’ for code. Our preliminary results provide suggestive evidence that these developers became more productive, completing 12.92% to 21.83% more pull requests per week at Microsoft and 7.51% to 8.69% at Accenture (depending on specification). Due to low compliance in the Microsoft experiment and internal organizational changes at Accenture, our estimates are not very precise and only reach statistical significance if we weight more heavily periods in which Copilot uptake differs across control and treatment.