Abstract: The two intravenous tox icity data for sodium valpro ate in mice, generated by using classical LD50 test, were compared.Though there were g reat differences betw een the tw o acute tox ic-itytest in testing time, bo dy weig ht, dosage, class interv al, and death distribution etc. the two LD₅₀ values were very close ( 1.14and 0.96 g/ kg ). It indicated that LD50 value as an evaluation index is st ill steady and repr esentative.