R. Alton Gilbert describes how the method of calculating this Bank’s adjusted monetary base is modified to reflect the timing of reserve accounting under contemporaneous reserve requirements. One important result of the change is that the reserve adjustment magnitude (RAM), the component of the adjusted monetary base that measures the effects of changes in reserve requirements, must be estimated for the most recent weekly observations. The adjusted monetary base for the most recent one or two weeks, therefore, will be preliminary. Past data indicate that errors in estimating RAM will be small.