In most situations, communication among parties involved in a group problem-solving situation is regarded as desirable if not essential, since each member's intentions can be made known and future actions made predictable. This experiment tested the hypothesis that communication facilitates the development of structure-in- interaction and thus contributes to the effectiveness of the group's problem-solving activities. The subjects, 120 women, most of whom were college graduates and ranged in age from 20 to 60 years, were divided into 30 groups of four members each. One-third were designated as Free Communication groups, another third as Limited Communication groups, and the final third as No Communication groups. The task for all groups was identical: to light a "goal square" in a 5 x 5 electrical plugboard in a minimum number of moves. Rules defining permissible moves were imposed to create a mutual task. The Free Communication groups were permitted to send a written message to any (all) of their partners between trials; the Limited Communication groups were required to send a message to each of their partners between trials; the No Communication groups were required to send a message to the experimenter at the end of each trial. Measures relating to task effectiveness showed the No Communication groups to be the most competent, the Free Communication groups next most competent, and the Limited groups least competent. This result was not anticipated. Detailed analysis suggests that under certain conditions group task performance may be hindered rather than facilitated by certain types of communication.