Several next-generation air-defense missiles will use dual-mode IR and rf guidance systems to address increasingly sophisticated threats. Performing hardware-in-the-loop tests of these systems to characterize IR and rf seeker performance, as well as developing and validating guidance algorithms, requires synchronously controlled IR and rf test targets, backgrounds, and countermeasures. The standard `electrically connected' approach uses separate IR and rf generation devices located in different laboratories and synchronized by a common control computer. This method has the disadvantage that the IR seeker must be physically removed from the guidance section and electrically reconnected via a long interface. The complex `collocated' approach combines IR and rf environment generators in the same enclosure, thereby eliminating the need for disassembly of the guidance section. A collocated IR/rf test facility is near completion at The Johns Hopkins University Applied Physics Laboratory. This article describes the new facility with emphasis on the IR environment simulator, which simulates targets, counter-measures, and background clutter.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.