Author obtained the following concentration of olfactory threshold of standard odors to 30 healthy persons (male : 15, female : 15 ; 18-25 years of ages), using a T&T type olfactometer. 1) On ""Detection threshold"", the concentration of each standard odors are 10^-5 in β-phenylethyl alcohol(A), 10^-5.2 in methyl cyclopentenolone(B), 10^-5.8 in isovaleric acid(C), 1^0-4.8 in γ-undecalactone(D) and 10^-6.1 in scatol(E). 2) On ""Recognition threshold"" the concentration of each standard odors are 10^-3.3 in A, 10^-3.7 in B, 10^-4.3 in C, 10^-3.2 in D and 10^-4.2 in E. 3) The concentration differences between ""Detection threshold"" and ""Recognition threshold"" were 10^1.7 in A, 10^1.5 in B, 10^1.5 in C, 10^1.9 in D and 10^1.9 in E. 4) Author was able to plot the olfactogram such a (Fig.3) in healthy persons, if the above concentration is the value of smelling loss ""0"" to standard odor.