As hydrazine, which is a strong reducing or anti-oxidant agent and quite toxic, becomes more and more widely used in industry and (as a propellant) in aerospace operations 87 interest continues to mount concerning its potential pollution of the environment and hazards to living organisms. One of the many potential problem areas receiving attention in the Air Force is hydrazine interaction with water and effects on aquatic organisms~ Two approaches were undertaken almost simultaneously in the early stage of this program. One was to determine the effect of hydrazine on various properties of water (pH, dissolved oxygen, alkalinity, hardness, etc.) prior to studying its toxicity to fish; the behavior of hydrazine compounds in water was investigated (SLONIM 1975), and the results on acute toxicity will be reported elsewhere. The other approach was to first develop a rapid and sensitive method for analyzing hydrazine in solution and second to apply it in studies to determine if hydrazine is stable or degrades in various types of aquatic systems. To meet the first requirement, a polarographic technique was developed recently that is highly specific for hydrazine, impervious to interfering substances, and relatively simple to perform (GISCLARD 1975). Second, this method was applied in this study to analyzing various water samples in which hydrazine was added and its concentration followed for four days. The results of five experiments are reported in this paper. Three experiments consisted of analyzing hydrazine in water taken from various outdoor sources and on-base facilities, the same samples equalized in terms of temperature and dissolved oxygen (DO), and water of varying hardness. The last two experiments involved the effect of fish excretions on hydrazine and some preliminary data on hydrazine uptake by fish.