Researchers of group creativity have noted problems such as social loafing, production blocking, and especially, evaluation apprehension. Thus, brainstorming techniques have specifically admonished people ‘not to criticize’ their own and others' ideas, a tenet that has gone unexamined. In contrast, there is research showing that dissent, debate and competing views have positive value, stimulating divergent and creative thought. Perhaps more importantly, we suggest that the permission to criticize and debate may encourage an atmosphere conducive to idea generation. In this experimental study, traditional brainstorming instructions, including the advice of not criticizing, were compared with instructions encouraging people to debate—even criticize. A third condition served as a control. This study was conducted both in the United States and in France. Results show the value of both types of instruction, but, in general, debate instructions were superior to traditional brainstorming instructions. Further, these findings hold across both cultures. Results are discussed in terms of the potential positive value of encouraging debate and controversy for idea generation. Copyright © 2004 John Wiley & Sons, Ltd.