The effects of GSS interface and task type on group interaction are examined in this experimental study. A 2 × 2 factorial design is employed. Each treatment has eight groups. Two types of GSS interfaces are studied: icon-based and text-based. Two task types are investigated: intellective and preference. Three dependent variables are measured: efficiency of influence attempts, inequality of influence attempts, and dominance significance. Results of data analysis show that groups using icon-based interface achieve greater efficiency of influence attempts, greater equality of influence attempts, and less dominance significance than groups using text-based interface. Moreover, equality of influence attempts is greater for preference task groups than intellective task groups. These results suggest that an icon-based interface is a useful feature of a GSS, particularly when group members are novice computer users. GSS developers should, therefore, pay attention to interface design on top of the considerations for other GSS features. © 1997 Elsevier Science B.V.