This study estimates the length of time that different economic segments take to respond to changes in the interest rate. The investigation ranges from January 1990 to June 1996, which includes the 'Collor' Plan and the two first years of the 'Real' Plan. In Brazil, the estimation of the response time to the monetary policy is based in American studies. This work intends to provide a better assessment of that. In the USA, the time society takes to react to monetary policy has been frequently estimated in a period of six to twelve months. This study found that in Brazil, depending on the segment (saving, consumption or production), the time of response is immediate, but it could take two or three months. The estimations were based on the cross-correlation between prewhitening variables by their own ARIMAS.