This is a paper on mixed integer linear programming models for short-term scheduling of batch plants as described by Pinto and Grossmann (1995, 1996). The models rely on continuous-time representation and make use of pre-ordering constraints, which can be either imposed as a separate set of constraints or can be included in the underlying representation for the model. We also describe the computer interface STBS which automatically formulates the models and generates solution outputs such as Gantt charts and order paths. As shown in the results, problems up to 50 orders in 25 machines and five stages can be solved in approximately 20 min. (C) 1998 Elsevier Science Ltd. All rights reserved.