This article tests whether agricultural extension and imperfect supervision-conflated here into the number of visits by a technical assistant-increase productivity in a sample of contract farming arrangements between a processing firm and small agricultural producers in Madagascar. Production functions are estimated which treat the number of visits by a technical assistant as an input and which exploit the variation in the number of visits between the contracted crops grown on a given plot by a specific grower, thereby accounting for district-, grower-, and plot-level unobserved heterogeneity. Results indicate that the elasticity of yield with respect to the number of visits lies between 1.3 and 1.7. © 2010 International Association of Agricultural Economists.