China operates the world's largest system of extension services, but knowledge about its effectiveness is limited. Using farm survey data and a stochastic meta-frontier production function, this study investigates the impact of extension services on the technical efficiency of crop-specific farms in China. Results reveal that extension services have a statistically significant and strongly correlated relationship with farm technical efficiency and that different sources of extension have an inconsistent impact on it. Crop-specific farms require distinct extension provision whose content is designed to match farmers' needs, and hence a pluralistic and well-functioning system of extension provision should be developed.