This paper addresses four ìstylized factsî that summarize data from experimental studies of voluntary contributions to provision of public goods. Theoretical propositions and testable hypotheses for voluntary contributions are derived from two models of social preferences, the inequity aversion model and the egocentric other-regarding preferences model. We Önd that the egocentric other-regarding preferences model with classical regularity properties can better account for the stylized facts than the inequity aversion model with non-classical properties.