Preventative maintenance is common in industry and aids in sustaining reliable process operations. If maintenance is executed within the production schedule, it imposes restrictions on the shared resources of the manufacturing facility. In multipurpose batch plants, these restrictions can affect many product pathways and have a significant impact on plant profitability. The combined optimization of process maintenance and production scheduling should therefore exploit the inherent flexibility of such plants and provide solutions with the highest profitability. This paper presents a mathematical model capable of addressing the combined scheduling of maintenance and production tasks within a continuous-time state-task network based framework. Multiple maintenance types are addressed within the framework. The proposed formulation is illustrated on an adaptation of a well cited literature problem, and the benefit of combined maintenance and production scheduling highlighted. (C) 2012 Elsevier Ltd. All rights reserved.