This is the sixth quarterly report of DOE Contract No. DE-AC22- 87PC79863, entitled Modeling of Integrated Environmental Control Systems for Coal-Fired Power Plants.'' This report summarizes accomplishments during the period January 1, 1989 to March 31, 1989. Efforts this past quarter focused primarily on the preparation of a computer User's Guide for the Integrated Environmental Control Model (IECM). Drafts of the first two chapters are now complete. These chapters constitute the bulk of this quarterly report. Drafts of the remaining chapters are in preparation, and will appear in a future report this year. We also have been working closely with DOE/PETC to define the computer configuration to be transferred to PETC as a contract deliverable. That process is now complete and the equipment is on order. Delivery of the IECM to PETC is expected during the next calendar quarter. Finally, we are continuing our efforts to develop and refine a number of clean coal technology process models. These efforts will be summarized and reported at a future date.