This paper studies a search-based model of OTC markets in which clients with heterogeneous trading needs direct their trades to one of ex-ante identical dealers. The main insight of the paper is that the way clients sort across dealers shapes dealer-to-dealer trading patterns and, in turn, generates a core–periphery interdealer network structure. Dealers in the model become heterogeneous because they attract different clients in equilibrium. Some dealers attract clients who trade frequently (e.g., index funds); others attract clients with infrequent trading needs (e.g., pension funds). Dealers attracting clients with frequent trading needs receive a larger volume of client orders, trade more with other dealers, and, as a result, form the core of the interdealer network. Conversely, dealers specializing in clients with infrequent trading needs form the periphery. I also show that accounting for client heterogeneity across dealers (a) challenges standard measurements and interpretations of bid–ask spreads and (b) generates predictions on bid–ask spreads and dealer centrality consistent with the empirical literature.

I build a search model of bond and credit default swap (CDS) markets with endogenous investor participation and show that shorting bonds through CDS increases the liquidity and price of bonds. By allowing investors to trade the credit risk of bonds without trading the bonds, CDS introduction expands the set of feasible trades and attracts investors into the credit market. Because search is nondirected within the credit market, new investors also trade bonds and consequently increase their price and liquidity. My results suggest that naked CDS bans increased sovereigns’ borrowing costs and thereby exacerbated the 2010–2012 European debt crisis.