The quantitative relationship between 2-methyl-4-amino-5-hydroxymethylpyrimidine (OMP) and vitamin B_6 was studied using running fit as an index. Toxicity tests of OMP and five other substances with a similar structure (I, II, III, X, XI) showed that (I) and (III) caused running fit as OMP. These two compounds were also found to be re1ated to vitamin B_6 (I), (II) and (III) intensified the toxicity of OMP.