Parties bound by an incomplete contract have an incentive to renegotiate after acquiring new information. The issue of the parties' investment in the relationship before renegotiation is analyzed in a simple two-period procurement model. The firm invests in the first period. It then learns its production cost, and the sponsor learns its value for the project. Williamson's underinvestment presumption is shown to hold under very general assumptions about bargaining and about the ex post asymmetry of information as long as the firm's investment is not observable by the sponsor. The introduction of a cancellation fee may well lead to even less investment contrary to what is sometimes argued. The role of ex ante price fixing as an alternative way to reintroduce some form of commitment and the problem of cost overruns are discussed. Last, it is shown that if investment is observable by the sponsor andthus may become a joint decision variable, the two parties may choose to under- or overinvest.