One of the most important problems in designing a cellular manufacturing system is the formation of machine cells and the grouping of parts. Most of the existing cell design procedures operate on a binary part-machine incidence matrix to identify block diagonality. Important factors such as part operation sequence and demand volume have not been commonly considered in past research. In this paper, a sequence-based materials flow procedure is developed to solve the cell formation problem. The new cell formation procedure is designed to consider operation sequences in accurately determining the costs of inter-cell movement, as well as forward and backward intra-cell movements. Extensive comparisons of the new cell formation procedure with the relevant existing procedures in the literature demonstrate the effectiveness of the new procedure.