This revised review presents the significant results of the recent studies on vitamin Bi. Among the most interesting discoveries is the part vitamin Bi plays in the formation of the enzyme cocarboxylase and the function of this enzyme. Surprising clinical results have been brought about by the use of massive doses of the vitamin in certain cases of ascites and edema associated with cardiac decompensation. Its toxicity has been shown to be so low that the danger from overdosage is nil. The role of the vitamin in plant physiology and culture is also presented. Each section carries abundant references, which enhance the value of the book for those wishing to consult original articles.