The purpose of this study was to investigate the effects of equality of varying degrees of influence exerted by individual members in the process of decision making upon decision time, perceived efficiency and perceived equality. Subjects were seventy-two university students and twenty-four three-person groups were formed. They made a decision on twelve words by selecting them from a word list in order to use them in a composition which they would subsequently write by group work. Observers judged the number of words decided by each member and this number served as the measure of the amount of influence exerted by each member. The index of equality of influence was defined by the same way as the equality of family income was defined with Lorenz curve in economics. The results showed that the greater the equality was, the more decision time was required and the lower the perceived efficiency was. It was also found that the greater the equality was, the larger the variance of decision time was and it suggested that in the case of decision making, in which members exerted influence almost equally, decision time was determined by some other factors in the members' interaction processes. As to the perceived equality, there were no differences among each level of equality. But, in the groups whose equality was considerably low, those members who exerted large influence perceived equality to be low and those members who exerted medium influence perceived equality to be high. From this result, it was considered necessary that such variables concerning individual members as perceived equality should be explained by both a set of variables representing the situation of group as a whole and a set of variables representing the situation of individual members.