We analyse the desirability of allowing cooperative banks to participate in the interbank market in Chile. We find that it is advisable to allow this if the quality of their governance is not too deficient relative to that of traditional commercial banks. When cooperative banks do participate in the interbank market, both the probability of financial crises and the volatility of gross domestic product (GDP) rise. However, because the inclusion of cooperatives generates large efficiency gains in the financial sector, both GDP and aggregate welfare substantially increase. We conclude that there is no policy reason to unilaterally exclude cooperatives from the Chilean interbank market.