LD_(50)测定是毒理学研究的重要组成部分。关于其测定方法国内已有资料详述。本文仅探讨LD_(50)的重演性、实验资料的统计处理、毒物的致死作用带及ET_(50)(1)等问题,现将结果报告如下,以供参考。一、LD_(50)的重演性LD_(50)有一定的波动范围。有人连续12年对26种化学物质每年重复测定大鼠经口LD_(50)由于某些实验条件的差异,重复测定的LD_(50)可有1～3倍的波动。据另一些报 LD_ (50) determination is an important part of toxicological research. About its determination of the domestic data have been detailed. This article only discusses the LD 50 duplication, the statistical processing of experimental data, lethal effect of poison and ET_ (50) (1) and other issues, the results reported below, for reference. First, LD_ (50) of the repetitive LD_ (50) have a certain range of fluctuations. Some people for 12 consecutive years of repeated determination of 26 kinds of chemical substances in rats oral LD_ (50) due to some experimental conditions, repeated determination of LD_ (50) can be 1 to 3 times the fluctuations. According to other newspapers