We study how the employment effects of enterprise zones vary with their location, implementation, and administration, based on evidence from California. We use new establishment-level data and geographic mapping methods, coupled with a survey of enterprise zone administrators. Overall, the evidence indicates that enterprise zones do not increase employment. However, the evidence also suggests that the enterprise zone program has a more favorable effect on employment in zones that have a lower share of manufacturing and in zones where managers report doing more marketing and outreach activities. On the other hand, devoting more effort to helping firms get hiring tax credits reduces or eliminates any positive employment effects, which may be attributable to idiosyncrasies of California's enterprise zone program during the period we study. (Contains 11 tables, 1 figure and 56 footnotes.)