Does formal contracting foster cooperation in a buyer-supplier relationship? In line with the literature, we find that a renegotiable contract with relationshipspecific joint investments does not make it possible to reach the first-best. However, we show that a renegotiable contract may induce more cooperation than an informal arrangement can. This result may help to understand how cooperation emerges in Japanese procurement practices, which typically involve relationshipspecific joint investments and renegotiable contracts.