Scientists have asserted that genetically modified (GM) food offers financial, environmental, health, and quality benefits to society, but the realization of such benefits depends on consumer acceptance of this new technology. Consumer concerns about GM food raise questions about what consumers know about GM food and to what extent this knowledge translates into their evaluations of GM products. The present research empirically examines the effect of both objective and subjective knowledge on perceived risk and, in turn, key consumer behaviors associated with GM food. The results reveal that objective knowledge about GM food significantly reduces performance and psychological risks, whereas subjective knowledge influences only physical risk, and the valence of that impact depends on the level of the consumer's objective knowledge. Furthermore, different risk types enhance consumers' information search and reduce their propensity to buy GM food. The overall findings thus suggest the need for cooperation among government, scientific institutions, and the food industry to foster effective communication strategies that increase consumers' objective knowledge, reduce their risk perceptions, and encourage consumer adoptions of GM technology. © 2007 Wiley Periodicals, Inc.