This paper presents a novel hybrid constraint logic programming (CLP) and MILP algorithm for scheduling complex multipurpose batch processes. The scheduling problem is decomposed into two sub-problems: first an aggregate planning problem is solved using an MILP model, and then a sequencing problem is solved using CLP techniques. The CLP model avoids the complexity of explicitly stating complete material balance constraints by instead using precedence constraints between batches to ensure the schedule is feasible. The efficiency of the algorithm is demonstrated with four examples and areas for future improvement are identified. © 2005 Published by Elsevier Ltd.