Liberalization of the energy market has put increasing pressure on both electricity producers and distributors for lower costs. Since maintenance is a major expense account, such companies hill be inclined to reduce maintenance budgets. At the same time, increased liability for nondelivered-energy increases the costs of sudden failure of a component. Transformers are such a component; they are often an essential link in the distribution network. In order to reconcile both decreasing maintenance spending and reliable service, condition-based maintenance (CBM) is often proposed. The basis of a successful application of CBM lies in obtaining information on transformers, so that, on the one hand, a critical condition will be noted early enough to take measures and, on the other hand, so that only minimal maintenance is being applied to transformers still in good condition. This paper will review a series of often mentioned techniques in order to assess what the value of this technique will be for CBM and whether it can be used for condition monitoring.