In this study, a mixed-model flow line sequencing problem is considered. A mixed-model flow line is a special case of production line where products are transported on a conveyor belt, and different models of the same product are intermixed on the same line. We have focused on product-fixed, rate-synchronous lines with variable launching. Our objective function is minimizing makespan. A heuristic algorithm based on Lagrangean relaxation is developed for the problem, and tested in terms of solution quality and computational efficiency. (c) 2006 Elsevier Ltd. All rights reserved.