The concept Of CO2 injection and dispersal in the mid-depth ocean presumes that associated environmental impacts can be minimized by rapid dilution of CO2 with large volumes of seawater. Toward this end, an international field experiment at an open ocean site is being planned to investigate the dispersion, dissolution, and transport phenomena Of CO2 ocean sequestration. To support this effort, complementary laboratory experiments are being pursued to examine CO2 droplet formation processes and to calibrate and to assess the performance of injector designs that will be used in the field experiment. The experiments reported in this paper were carried out in laboratory facilities at the University of Hawaii, the Southwest Research Institute, and in Japan that can simulate conditions in the deep ocean. Liquid CO2 was injected through a variety of removable, single and multiple orifice injectors mounted in pressure vessels filled with salt water. Injection velocity was varied and measurements of the resulting droplets were performed. Tests also were conducted to address operational concerns about possible hydrate blockage of injector orifices and the submerged CO2 conduit during system start-up and shutdown. (c) 2004 Elsevier Ltd. All rights reserved.