More and more machines are getting equipped with sensors whose data are transformed into machine conditions (degradation levels). Monitoring machine conditions enables to maintain machines before they fail without replacing expensive components too soon. A machine builder or maintenance service provider can use the conditions of its customers’ machines for planning their maintenance actions more efficiently. However, the conditions of the machines also provide information on future demand for spare parts. The objective of this PhD research is to develop better spare parts management strategies that exploit this so-called advance demand information.