This document summarizes a study on factors that influence teachers' professional development at work. The study used questionnaires to examine how organizational and task factors relate to teachers' participation in learning activities and development of occupational expertise. Regression analysis found that reflection/feedback activities were predicted by work pressure, social support from colleagues, and value of tasks. Collaboration was predicted by work pressure, social support from colleagues/supervisor, and tasks beyond teaching. The study concludes schools must organize support for teacher learning.