In this paper, we investigate the role of formal and relational contracts in managing alliance risks that arise in co-opetitive collaborations. We undertake a case study of a co-opetitive sales alliance within the independent publishing sector, incorporating data from all firms to the alliance. We provide empirical evidence of the relational risks of misappropriation and opportunism as manifest in both vertical (buyer-supplier) and horizontal activities within the alliance and identify a further relational risk relating to concerns of introducing homogeneity into the product offerings of firms. We also examine the nature of compliance and regulatory risk, which is salient in this setting given the potential for anti-competitive behaviour towards customers and suppliers. We find that the firms mitigate alliance risks primarily through the use of relational contracts (informal self-enforcing agreements). Formal contracts are evident in the buyer-supplier relationship, but are used mainly for ex post co-ordination. We adopt an organisational economics perspective to explain the specific mechanisms that support