The study of household finance is challenging because household behavior is difficult to measure, and households face constraints not captured by textbook models. Evidence on participation, diversification, and mortgage refinancing suggests that many households invest effectively, but a minority make significant mistakes. This minority appears to be poorer and less well educated than the majority of more successful investors. There is some evidence that households understand their own limitations and avoid financial strategies for which they feel unqualified. Some financial products involve a cross-subsidy from naive to sophisticated households, and this can inhibit welfare-improving financial innovation.A PRESIDENTIAL ADDRESS IS A PRIVILEGED OPPORTUNITY to ask questions without answering them, and to suggest answers without proving them. I use this opportunity to explore a field, household finance, that has attracted much recent interest but still lacks definition and status within our profession. Teaching and research are presently organized primarily around the traditional fields of asset pricing and corporate finance. Economists in the former field ask how asset prices are determined in capital markets and how average asset returns ref lect risk. Economists in the latter field ask how business enterprises use financial instruments to further the interests of their owners, and in particular to resolve agency problems.By analogy with corporate finance, household finance asks how households use financial instruments to attain their objectives. Household financial problems have many special features that give the field its character. Households must plan over long but finite horizons; they have important nontraded assets, notably their human capital; they hold illiquid assets, notably housing; they face constraints on their ability to borrow; and they are subject to complex taxation.