In the last 60 years different efforts have been made for the construction of a metro system in Bogotá yet the closer the city has got to building a large transport project was with the implementation of a Bus Rapid Transport System in 1999 called Transmilenio. Transmilenio was a success at the beginning and it helped organize the chaotic transport system of the city, but at the moment it is suffering from capacity and operational problems and the need for a rail base system is evident. The current governments of Bogotá and Colombia have promised to begin the construction of the first line of the metro in the following years. Bogotá and London are two cities with similar characteristics such as population, area, density and type of soil; furthermore both cities are in the process of building a new mass transport system; in Bogotá the first line of the metro and in London Crossrail. London is a pioneer city in railways and metro systems in the world and has experience on the economic appraisal of this type of projects. In this dissertation we will use this experience to elaborate a Cost and Benefit Analysis model for the Bogotá metro. Cost and Benefit Analysis models are a common tool for the appraisal of transport and infrastructure project around the world and particularly in the UK. We have elaborated an appraisal tool for the decision makers of Colombia that involves the more important technical, social and economical aspects of the Bogotá metro project. After the evaluation of all the cost and benefits of the system and the preparation of a model with 3 different scenarios and 7 sensitivity tests the results shows that the project is completely feasible, it should be constructed and will bring benefits for the Colombian society.