In Alzheimer's disease and related disorders estimates of informal care costs have been neglected and when included in cost of illness studies, valuations have been highly variable. This illustrates the need to standardise the methodology not only for valuing formal, but also informal care costs. Methods used for valuing informal care are identified, together with theoretical and practical challenges in measurement. In particular the measurement of time and it's associated satisfaction or utility is complex and valuations of time need to consider aspects of the caregiving experience which influence the marginal valuation of the time spent caring. Argues that more empirical work is required to elicit information on both the positive and negative satisfaction associated with caregiving and to incorporate this into valuations of the costs related to informal care.