This May I was invited by my lT colleagues at the University of Tennessee to give a presentation on the importance of Top-Down & Bottom- Up forecasting in the Sales and Operations Planning (S&OP) process. The last time I had covered this type of forecasting in one of my columns was eight years ago in the Summer 1998 issue of The Journal of Business Forecasting (JBF). Its title was “A Simple View of Top-Down Versus Bottom-Up Forecasting.” When I wrote that piece, I felt I had given the topic the coverage it needed for a very long time. However, having to prepare for this year’s presentation opened my eyes to the fact that, since I wrote that article eight years ago, much has changed. The topic of Top-Down & Bottom-Up forecasting has become even more important.