The essays in this volume explore different aspects of interest rate theory. They investigate how to model forward rates and short rates, how to invert the yield curve, and how to price contingent claims. The researchers use various mathematical models to analyze the term structure of interest rates and compare different approaches. They find that different models can generate similar yield curves and forward rate curves. Additionally, they present a new solution to the term structure equation that deviates from standard conditions but still provides a quasi arbitrage-free term structure.