:The 60-Day and 90-Day closed manned chamber tests conducted by the McDonnell Douglas Corporation in the 1960s have been thoroughly reported in the literature. These tests evaluated, among other things, the leading water recycling systems developed at that time. During both tests, crew members ingested water reclaimed from urine and humidity condensate and performed personal hygiene tasks with water recycled in a separate loop. Since then, to this date (1995), no comparable testing has been carried out in the United States. Now, however, plans are being made to test modern water recycling systems in chamber tests with humans. This paper summarizes the earlier testing and highlights the lessons that were learned.