Utility theory is interested in people's preferences or values and with assumptions about a person's preferences that enable them to be represented in numerically useful ways. The first two sections of this paper say more about what utility is, why people are interested in it, and how it is interpreted and used in the management and behavioral sciences. The third section summarizes a number of utility theories: it may be used either as a concluding overview of the range and variety of utility theories or as a bridge to the final sections. The final eight sections comprise a semi-technical survey of particular theories for readers interested in greater depth.