ABSTRACTWhen capital market investors and firm insiders possess the same information about a company's prospects, its liabilities will be priced in a way that makes the firm indifferent to the composition of its financial liabilities (at least under certain, well‐known circumstances). However, if firm insiders are systematically better informed than outside investors, they will choose to issue those types of securities that the market appears to overvalue most. Knowing this, rational investors will try to infer the insiders' information from the firm's financial structure. This paper evaluates the extent to which a firm's choice of risky debt maturity can signal insiders' information about firm quality. If financial market transactions are costless, a firm's financial structure cannot provide a valid signal. With positive transaction costs, however, high‐quality firms can sometimes effectively signal their true quality to the market. The existence of a signalling equilibrium is shown to depend on the (exogenous) distribution of firms' quality and the magnitude of underwriting costs for corporate d