This paper presents an interactive procedure for solving a multiple attribute group decision making (MAGDM) problem with incomplete information. The main properties of the procedure are: (1) Each decision maker is asked to express his/her preference in relation to an additive value model with incomplete preference statements. (2) A range-typed representation method for utility is used. The range-typed utility representation makes it easy to compare each group member's utility information with a group's one and to aggregate each group member's utility information into a group's one. Utility range is calculated from each group member's incomplete information. (3) An interactive procedure is provided to help the group reach a consensus. It helps each group member to modify or complete his/her utility with ease compared to group's utility range. (4) We formally describe theoretic models for establishing group's pairwise dominance relations with group's utility range by using a separable linear programming technique. (C) 1999 Elsevier Science B.V. All rights reserved.