Book excerpt: Black and Scholes (1973) and Merton (1974) (hereafter referred to as BSM) introduced the contingent claim approach (CCA) to the valuation of corporate debt and equity. The BSM modeling framework is also named the 'structural' approach to risky debt valuation. The CCA approach considers all stakeholders of the corporation as holding contingent claims on the assets of the corporation. Each claim holder has different priorities, maturities and conditions for payouts. It is based on the principle that all the assets belong to all the liability holders.In the structural approach the arrival of the default event relies on economic arguments for why firms default as it is explicitly related to the dynamics of the economic value of the firm. A standard structural model of default timing assumes that a corporation defaults when its assets drop to a sufficiently low level relative to its liabilities.The BSM modeling framework gives the basic fundamental version of the structural model where default is assumed to occur when the net asset value of the firm at the maturity of the pure-discount debt becomes negative, i.e., market value of the assets of the firm falls below the market value of the firm's liabilities. In a regime of limited liability, the shareholders of the firm have the option to default on the firm's debt. Equity can be viewed as a European call option on the firm's assets with a strike price equal to the face value of the firm's debt. Actually, CCA can be used to value all the components of the firm's liabilities. Option pricing models are used to value stocks, bonds, and many other types of corporate claims.Different versions of the model correspond to different assumptions about the conditions when a firm defaults. Merton (1974) assumes that the firm only defaults at the maturity date of the firm's outstanding debt when the net asset value of the firm, in market value terms, is negative. Others introduce other conditions for default. Also, different authors introduce more complicated capital structure with different kinds of bonds (e.g. senior and junior), warrants, corporate taxes, ESOP, and more. Volume 1: Foundations of CCA and Equity ValuationVolume 1 presents the seminal papers of Black and Scholes (1973) and Merton (1973, 1974). This volume also includes papers that specifically price equity as a call option on the corporation. It introduces warrants, convertible bonds and taxation as contingent claims on the corporation. It highlights the strong relationship between the CCA and the Modigliani-Miller (M&M) Theorems, and the relation to the Capital Assets Pricing Model (CAPM). Volume 2: CCA Approach to Corporate Debt ValuationVolume 2 concentrates on corporate bond valuation by introducing various types of bonds with different covenants as well as introducing various conditions that trigger default. While empirical evidence indicates that the simple Merton's model underestimates the credit spreads, additional risk factors like jumps can be used to resolve it. Volume 3: Issues in Corporate Finance with CCA ApproachVolume 3 includes papers that look at issues in corporate finance that can be explained with the CCA approach. These issues include the effect of dividend policy on the valuation of debt and equity, the pricing of employee stock options and many other issues of corporate governance. Volume 4: CCA Approach to Banking and Financial IntermediationVolume 4 focuses on the application of the contingent claim approach to banks and other financial intermediaries. Regulation of the banking industry led to the creation of new financial securities (e.g., CoCos) and new types of stakeholders (e.g., deposit insurers).