The aim of this work is to establish the relationshipbetween the Colombian business cycle and monetary policy through the study ofthe natural real interest rate. Pair this purpose, we calculate the naturalreal interest rate (TIRN) for Colombia using two different methodologies. Once the natural real interest rate, an analysis of the effects of monetary policy over the business cycle in Colombia, based on the Neowicksellianas. It is concluded that the gap, due to the difference in market interest rates and natural, have effects on the Colombian business cycle causing changes in GDP.