Spanish Abstract: En esta monografia se analiza el coste del capital de la empresa. En concreto: que es, que factores lo determinan, que supuestos basicos son necesarios para su calculo, el coste de las deudas, acciones preferentes y acciones ordinarias, y el coste del capital medio ponderado.English Abstract: In this monograph the cost of capital of firm is analyzed. It studies: what is the cost of capital, what factors determine it, in what basic suppositions it is based, how to obtain the cost of debt, preferent shares and ordinary shares, and what is the weighted average cost of capital (WACC).