When consumer choice is constrained by time as well as money, willingness to pay can be defined with respect to either numeraire. The two measures can be related formally within a utility-consistent model of choice subject to two constraints. Furthermore, when information is collected on both, the respondent's marginal value of time can be identified. A system of willingness to pay time and money and the marginal value of leisure time is estimated jointly in an application to California whalewatching and whale stock enhancement. The empirical approach can be applied with only minor additions to survey techniques for nonmarket valuation. Copyright 2004, Oxford University Press.