The present study was undertaken to gain more insight into the flocculation of oil-in-water emulsions by excess surfactant. A technique is employed to form reasonably uniform emulsions whose droplet size can be controlled over the range of about 0.2-2.5 pm. This allows separation of emulsifier effects on stability from those associated with formation. The results presented below indicate that surfactant-induced flocculation is observed for a variety of surfactant structures, depends strongly on droplet size, and is consistent with theoretical calculations of depletion flocculation.