This is the final report for the Department of Energy Contract No. DE-AC21-76-ET10256, Developing/Modifying Coal Grinding Procedures and Equipment to Produce Predictable Size Distributions During Coal Preparation. Four unit operations for size reducing coal have been examined. These are: air swept ball mill, air swept hammer mill, air swept ball and race mill, and wet ball mill. The project work was broken up into four phases - Study Phase, Preparation Phase, Testing Phase and Reporting Phase. The Study Phase resulted in a state-of-the-art study of coal size reduction devices, the selection of representative coal samples and the laboratory development of grinding kinetics for the selected coals. The Preparation Phase work centered on the layout and preparation of a pilot scale testing facility for generating continuous industrial type size reduction data for the validation of laboratory generated findings. Work under the Testing Phase involved test equipment modification, conducting experiments and the collection and reduction of data. The Reporting Phase resulted in this final report and the ERDA/DOE Publication Coal Grinding Technology, A Manual for Process Engineers (Document No. FE-2475-25). Progress throughout the project was documented with monthly, quarterly and annual progress reports. Some 350 coal grinding tests were performed. The reduction of this test data has aided in the development and validation of mathematical models which can be used to analyze and predict the performance of size reduction devices of the types studied here. In addition, the information generated has led to a number of recommendations for expanding the current state of knowledge of coal size reduction.