The comparative toxicity of halogen-containing oxidizing agents was investigated with the purpose of their utilization as urine preservatives in water reclamation systems. It was found that the high toxicity of the agents (LD50 of agent 1 was 15.7 +/- 1.1 mg/kg and LD50 of agent 2 was 23.0 +/- 1.2 mg/kg when injected i.p. to white mice) was distinctly related to their low pH in water solutions (pH 3-4). In neutral solutions the toxicity of agent 1 decreased 35 times and that of agent 2-12 times so that they can be classified as moderately toxic substances. Using an isolated frog heart according to Straub, it was shown that solution neutralization with 20% NaHCO3 also decreased the toxic effect of the above agents, making them similar to chloramine B, a well-known disinfectant. The above agents were found to be rapidly inactivated when stored in low concentrations and to remain highly stable when stored in concentrated solutions.