The growth activities of thiamine, its derivatives, pyrimidines and thiazoles on thiamine requiring mutant strains of E. coli are described. The pre-incubation of inoculum in glucose-phosphate solution has effects on the growth activities of thiamine and its moieties. Present experiments lead to the conclusion that many thiamine related compounds tested exert more characteristic influences on the growth of thiamine-less mutants than that of the wild-strain. The essential substituent of pyrimidine ring for activity is an NH_2 group at position 4 ; at 5 -CH_2OH, -CH_2NH_2 and -CHO permit the growth of pyrimidine-less mutant but -H, -CN and -COOH inhibit the growth. For the biological activities of the thiazole, the -CH_2CH_2OH at 5 seems to be essential ; -CH_2CH_2OCOCH_3 inhibits the growth of pyrimidine-less mutants. The -H at 2 is replaceable by = S or = H_2 but not by -NH_2 or -OH.