This article presents the findings of the Professional Assessment and Comprehensive Evaluation System (PACES) Spring 2000 Fields Study in a large southeastern school district. PACES is a comprehensive, learner-centered, classroom-based system that is designed to provide teachers, administrators, and other educators with information useful for improving teaching and learning. PACES teaching and learning can take a variety of forms including: teacher self-assessment, assessment of written planning documents, collaborative conversations about teaching and learning, group assessments by teachers working together to share their views, and assessments resulting form one or more systematic classroom observations and professional conferences. During the 2000 Field Study, PACES was undergoing its first year of district-wide piloting. Semi-structured interview data were collected from 205 in-school personnel (teachers, administrators, and union stewards) at 24 different school sites. The results of the study provide valuable administrative insight into organizational change processes, issues of school culture and change, and reform and improvement of teacher assessment and evaluation practices. The article begins with a brief history and description of PACES. The details of the 1999-2000 school year pilot of PACES are then described. The methods used in the study are explained, including scholarship supporting the research methodology employed for the study. The results of the study are presented, followed by a set of recommendations that are designed to facilitate the successful implementation of a new teacher assessment system. © 2000 Kluwer Academic Publishers.