Increasing numbers of semiconductor manufacturers are implementing improvement programs at their manufacturing sites (fabs). Yet despite their rising popularity, little attention has focused on the impact of a program's design on its overall effectiveness. This research examines the improvement programs established at ten fabs. A categorization scheme classifies programs according to their use of one of three types of teams: continuous improvement teams (CIT's), quality circles (QC's), and self-directed work teams (SDWT's). Results from 188 operator surveys and over 150 interviews with fab employees (including managers, engineers, technicians, supervisors, operators, and representatives from human resources and quality departments) indicate that a number of programs suffer from weak implementation and disorganized management. The failure to carefully design and implement a program is reflected in employee perceptions of the program's effectiveness. Perceptions of CIT programs are found to be significantly lower than those of QC or SDWT programs, both of which feature higher degrees of autonomy and training. Results also highlight a nearly universal failure to integrate production team programs with engineering and maintenance functions. To help improve future programs, design implications and aspects of effective team programs are noted. Special attention is paid to program selection, goal design, organizational support, engineering integration, information systems, and empowerment semantics.