This paper briefly describes two projects--one in the United States, one in England--that studied professional learning communities (PLCs). Part I of the paper describes the two projects. The American project is called the Creating Communities of Continuous Inquiry and Improvement project. The purpose of this study was to document and examine evidence of efforts taking place in American schools actively engaged in creating PLCs. The English project, Creating and Sustaining Effective Professional Learning Communities, set out to identify and provide practical examples of the following: characteristics of effective PLCs in different kinds of schools; key factors inside and outside schools that seem to help or hinder the development of PLCs; and innovative practices for ongoing professional learning and development. Part II of the paper discusses the commonalities of the two projects. Part III discusses emerging research issues stemming from the projects from the both the American and English perspectives. Appended are a heuristic model of a professional learning community, an assessment instrument, a description of research protocol, a matrix of a PLC organizer, and a list of PLC dimensions and critical attributes. (WFA)