Project MAFEX (Meta-Analysis of Field Experience) used standard meta-analysis techniques to synthesize the available body of research concerning preservice field experience programs. Several important questions were considered: (1) What types of field experience programs are most and least effective? (2) Are there common characteristics of field based programs that affect students consistently in all areas? and (3) How do field experiences in methods courses compare to field experiences in other areas of study? These programs were assessed in relation to preservice teacher attitudes, achievement, delayed outcomes, and teaching behavior. Consistent findings indicate that field experiences are generally positive experiences in general education courses, methods courses, and science methods courses. Attitudes, achievement, and teacher behavior, however, are not affected equally in all courses. In addition, duration studies of field experience indicate that few to moderate numbers of field experiences tend to have positive effects on preservice teachers. Conversely, exposure of students to many field experiences appears to dramatically diminish previous gains on desired outcomes. Eleven tables and a four-page bibliography are appended. (Author/JMK)