A method for the calculation of mesoscale convective system (MCS) precipitation efficiency (PE) is presented. For eliminated precipitation (Mp), 4 km grids of precipitation based upon rain gauge reports and radar estimates are obtained from the National Centers for Environmental Prediction (NCEP); these are available for 6 hour periods. For ingested moisture (Mi), hourly surface airways reports were objectively analyzed (Barnes) to a 40 km grid proportioned to fit the 4 km NCEP grid. The moisture flux divergence was then calculated from the 40 km grids and then integrated in time and for the geographical area affected by the MCS. Further details will be supplied on the PE calculation method, as will examples of MCS PE using the method. Calculated PEs will then be related to GOES soundings both qualitatively (profile typing) and quantitatively (statistically linking profile variables like CAPE to calculated PEs).