Formative assessment, in this article, is defined as “the process used by teachers and students to recognize and respond to student learning in order to enhance that learning, during the learning.” The findings of a two-year research project in New Zealand indicate that formative assessment has the following characteristics: responsiveness, sources of evidence, a tacit process, using professional knowledge and experiences, an integral part of teaching and learning, formative assessment is done by both teachers and students, the purposes for formative assessment, the contextualized nature of the process, dilemmas, and student disclosure. © 2001 John Wiley & Sons, Inc. Sci Ed85:536–553, 2001.