Research has shown that individuals produce fewer ideas in interactive brainstorming groups than when brainstorming alone. However, group brainstorming remains a popular technique in organizations and industry. One basis for this popularity may be the perceived productivity of group brainstorming. A survey of expected performance in group brainstorming revealed that most individuals believed they would generate more ideas in groups than alone. Individuals who, in a second experiment, actually performed in brainstorming groups also perceived their performance more favorably than individuals who brainstormed alone. The results of a third experiment indicate that the illusion of group productivity may derive in part from the opportunity for social comparison that is available in group brainstorming. It also appears that individuals tend to take credit for a disproportionate amount of the brainstorming activity in groups.