A growing number of initiatives around the country are attempting to expose students to hands-on computer science (CS) curriculum and courses--and to address documented disparities in CS education. Answering the call for computer science expansion and equity, the New York City Department of Education (NYCDOE) launched the CS4All initiative in 2015, with the goal of providing meaningful, high-quality computer science education to all NYC public school students at each grade band (i.e., K-2, 3-5, 6-8, 9-12) by 2025. CS4All aims to provide professional development (PD) in CS for nearly 5,000 teachers, specifically targeting those with little or no computer science background. The initiative is focused in part on increasing access to CS education among students from historically underrepresented groups, including girls, Black and Latino students, English Learners, and special education students. The Research Alliance for New York City Schools, in partnership with the Education Development Center (EDC), is conducting a multi-year evaluation of CS4All to assess the implementation of the initiative across the district; examine its impact on schools, teachers and students; and provide information that supports the continuous improvement of the initiative over time. The report describes findings from the first year of the evaluation. It presents: (1) The overarching goals of CS4All and the primary strategies for pursuing those goals; (2) A broad picture of CS education and training in the City--including programs that are the result of CS4All's early implementation, as well as preexisting efforts; and (3) Teacher responses to CS4All PD, including the extent to which they report implementing what they learned. The report draws on these findings to suggest a number of recommendations for the district to consider as it continues to develop the CS4All initiative. [For the Technical Appendices to this report, see ED591502. Support for the study also came from the CS4All Founders Committee.]