Creating a forecast for a new pharmaceutical is daunting but exciting. The forecast is likely to be driven by just a few key assumptions: the treatable patient population, the peak market shares of competing products, and how quickly products achieve these peak market shares — their uptake rate. Getting these assumptions “right” is paramount to an accurate forecast. This short series of papers will dissect pharma uptake curves and the unique forecasting challenges you will likely face. We start by introducing the Bass model.