This paper firstly discusses the make-to-order (MTO) manufacturing sector to show the different types of queuing network that may exist and need to be covered. The workload control (WLC) production planning method is modelled as a queuing network with limited buffer capacities in front of each workstation. Exact solutions for a general network with more than 3 or 4 workstations are not possible. An approximation algorithm, as an extension of earlier work on simple tandem queuing networks, has been developed to cope with any number of workstations and to allow flows forwards and backwards between the workstations. The essentials of the model and solution algorithm are briefly described. The second half of the paper presents the results of using the model and algorithm to analyse four issues in WLC in MTO. The first set of experiments examines the relative value of two WLC mechanisms for controlling manufacturing lead times, job release and order acceptance. The second set of experiments is to gain insight into how increased complexity in production layouts and the product variety impact on manufacturing performance measures. The third set of experiments examines the differential effects of extra buffer capacity at earlier or later workstations in the main path flow; whilst the final set of experiments examines the impact of having groups of high- and low-priority jobs. (C) 2003 Elsevier B.V. All rights reserved.