In this paper we provide empirical evidence consistent with the hypothesis that options market makers face risks in managing inventory that are unique to the options markets. In particular, we show that risks associated with the inability to rebalance an option position continuously and uncertainty about the return volatility of the underlying stock each account for a statistically and economically significant proportion of the bid-ask spreads quoted for a sample of Chicago Board Options Exchange options.

Exchange members claim that the professional relationships that evolve on exchange floors yield benefits not easily duplicated by an anonymous exchange mechanism. We show that longstanding relationships between brokers and specialists can mitigate the effects of asymmetric information. Moreover, a specialist who actively attempts to differentiate between informed and uninformed traders can achieve equilibria that Pareto-dominate an equilibrium in which the two types of trades are pooled. Our model also elucidates the role of block trading houses in mitigating information problems in the block market.