By a series of toxicological experiments, including studies on chronic toxicity, teratogenesis and reproduction, Ames’ assay and carcinogenic observation, the non-effective level of tetrachlorvinphos (TCVP) was determined to be 0.15 mg/kg wt. Based on this, the acceptable daily intake for an adult was calculated to be 0.9 mg, including 9% (i.e. 0.081 mg) from drinking water. If an adult takes 3 liters of water per day, the concentration of TCVP in water should be 0.027 mg/1, approximately 0.03 mg/1. Both the requirements of the effects of TCVP on the organoleptic characteristics and self-purification processes in surface water can also be satisfied with 0.03 mg/1. Thus, the authors suggest that the maximum permissible concentration of TCVP in surface water could be established as 0.03 mg/1.