Significant modifications were made to the basic cost algorithms contained within ASPEN to achieve better base cost estimates. This was done as part of a DOE - METC contract to prepare a simulation model for the Great Plains plant. Also, a default set of parameters was developed to establish bulk material and construction labor (OE) cost factors as a function of equipment cost, based on in-house quotations and equipment purchased for petrochemical plants, for a large number of equipment items. The equipment items for which these factors were added are: air coolers, compressors, fired heaters, heat exchangers, pressure vessels, pumps, storage tanks, and towers. In addition to seven OE categories already in ASPEN, piping, concrete, steel, instruments electrical, insulation, and painting, three new categories were added: building, erection, and fireproofing.