The article examines the relationship between the demand of the system and the fares and costs of TransMilenio and the competing modes as well as other demographic and economic variables, after analysing data in a multiple linear regression model. The results suggest that demand has increased mainly as a result of the strong economic and population growth. It concludes that the demand is being severely affected by competition from the traditional bus system. Little can be done if the latter is not reformed and integrated with TransMilenio in a network covering the entire