As a disulfide form B(1), namely, thiamine tetrahydrofurfuryldisulfide (TTFD) possessing tetrahydrofurfuryl group, has been synthesized on the heel of alkyldisulfide form B(1) derivatives such as thiamine propyldisulfide (TPD) and thiamine oxyethyldisulfide (TOED), etc, the author with purpose to compare B(1)-effects not only of TTFD, but also of TPD and TOED, carried out a series of experiments on the prevention of B(1) deficiency in lovebirds. For the test animals 28 lovebirds weighing about 12g each and fed on the routine feed for one week were divided into 5 groups, and they were then fed on B(1) deficient standard feed. One group was taken as the control, and each of four other groups was daily fed orally on 0.006μM of B(1), TPD, TOED and TTFD respectively at a given time for 16-17 days. Next, the daily dose of each was cut down to 0.003μM, and the daily body weight and the length of survival time were recorded. The dose of 0.006μM is equivalent to about 2γ B(1). The experiments were repeated twice, and in the second series tow birds selected from each group on the eleventh day, namely, on the day just before the vitamin B(1)-deficient group died of cramps, were sacrificed, and the total B(1) contents in the liver, heart and brain were estimated. The quantitative analysis of B(1) was carried out by the thiochrome method and estimated by Coleman's fluorescent spectroscope. The duration of survival in the B(1)-deficient group was on the average of 8.8 days, while that given B(1), TPD, and TTFD was on the average of 16.4, 202, and 17.0 days respectively. The total B(1)-contents in the organs were 59.0γ, 119.0μ, and 79.6γ in the liver, heart and brain respectively. In the groups administered B(1), TPD, and TTFD, the contents in the liver of each were 259.1γ, 251.1γ, and 206.2γ; in the heart, 289. 2γ, 242.3γ, and 228.5γ; and in the brain, 135.2γ, 145.6γ and 121.9γ respectively. Among the groups given B1-derivative there is no significant difference, but the groups given B(1), the B(1)-content of the heart is somewhat greater while the B(1)-contents of the liver, heart and brain in TTFD group were slightly lower than in other groups. 1. From these it has been confirmed that TPD, TOED, and TTFD like B(1) all prolong the span of life and show the effect preventing B(1) deficiency. 2. Among them the preventive effect of TPD is most marked, while the other B(1)-derivatives show the effect not greatly different from that of B(1). 3. On estimating values of B(1)-contents in the organs of the each gruop on the eleventh day, the tissue B(1)-contents of the liver, heart and brain in TTFD group were somewhat less than these in B(1)-group or in TPD group.