The paper details the ongoing collaboration between the U.S. EPA and the U.S. Army Corps of Engineers in the development of complementary microcomputer based cost estimating systems for hazardous waste remediations. The U.S. EPA system, 'Remedial Action Cost Estimating System' (RACES), is a technology based application. Estimates generated by RACES are based upon cost engineering relationships. The estimates are designed for use in the early stages of remediation design. The U.S. Army Corps of Engineers system, 'Micro-Computer Aided Cost Engineering System' (M-CACES), is a 'bottoms-up' system for use in situations where detailed design information is available. While both systems will stand alone, they have been designed to allow the transfer of estimates generated by RACES directly into the M-CACES system.