Our study investigates the antecedents and performance implications of cooperative exchange norms. We argue that, in early relationships, the level of expected cooperative norms in an exchange is the result of a calculative process facilitated by transaction attributes: joint transaction-specific investments and observability. The greater the level of these two exchange attributes, the greater the level of cooperative exchange norms, all else being equal. We further argue that the realized level of cooperative exchange norms can deviate from the expected level because the development of such norms is the result of social processes that management cannot directly and fully control. This gap between realized and expected norms affects exchange performance. Performance suffers when the realized level of cooperative exchange norms falls below the expected level, but overshooting expectations lays a critical groundwork for repeat transactions. The analysis of a survey of 182 collaborative R&D alliances provides initial support for our theory.