In 2003, after three pilot projects successfully implemented WHO's Health-Promoting Schools (HPS) concept, officials in Zhejiang Province, China, expanded to additional 51 schools (93,000 students and their families and 6800 school personnel). Each school identified a health issue to begin HPS development, followed by conceptual orientation, resource mobilization, teacher training, surveys, interventions, outreach and evaluation. This study focused on the extent to which participating schools implemented the HPS concept and improved their psycho-social environments (PSEs). Forty-nine of the 51 schools met China's HPS criteria. Schools with fewer resources and with substantial resources, i.e. schools in both rural and urban areas, met the criteria. Schools' PSEs, as measured by the PSE Profile, improved as they became HPS. Findings from interviews and observations identified strong encouragement and support from officials, school personnel, students, parents and community leaders, and consistency of HPS with the national policy on quality education, as success factors.