Monetary policy has been aggressively used by the central Bank of Pakistan, in this decade, first to bolster growth and then to contain rampant inflation. Despite the sufficiently tight monetary policy that has remained in vogue in recent times, the inflation is still around 20 percent. This has raised questions about the effectiveness of monetary policy. One possible reason for the lesser effectiveness, if not failure, of monetary policy in taming inflation could be that in recent times, inflation was primarily supply driven and that the monetary tightening was in part offset by fiscal expansion, on the back of heavy bank borrowing by the government. However one cannot rule out the possibility that market imperfections might have also impeded the effectiveness of monetary policy in taming inflation to the desired extent. Incomplete and slow pass through of changes in policy interest rate to deposit rate and lending rate is a kind of imperfection that constrains the effectiveness of monetary policy. This study examines the pass through of policy interest rate to different market rates. Monetary theory predicts that the change in policy interest rate influences the cost capital which in turn influences consumption, savings, investments, and hence output. However if the impact of the change in policy rate on the cost of capital is less than one for one or if the change in policy rate fails to influence the cost capital immediately then the impact on output would become visible only with a certain lag and the impact would be less than one for one. This implies that if for example only 70 percent of the change in policy rate is passed on to cost of capital, then to manage an increase of 100 basis points in cost capital the policy rate should be raised by 143 basis points. This example serves to emphasise that for effective monetary management knowledge of the magnitude of passthrough of policy rate and the lag structure with which the policy rate influences cost of capital is important. Substantive empirical evidence confirms that changes in policy interest rate are transmitted to the output with a certain lag and that the pass-through of changes in policy rate to output or to other elements of the transmission channel may be less than one for one. Given the policy implications of the information, on the magnitude of pass through and the lag structure with which the policy rate influences different market rates, this Paper seeks to measure the pass-through of the changes in six month Treasury bill rate to six month KIBOR, six month weighted average deposit rate and weighted average lending rate. The study is focused on Pakistan.