Biomass gasification with pure steam in a fluidized bed is a highly endothermal process that has been connected in several ways to a fluidized-bed combustor to burn the char that is generated in the gasifier. This resulted in what currently is called dual fluidized-bed (DFB) biomass gasifiers. This review starts by describing the pioneering DFB biomass gasifiers that were operated during the period of 1975-1990 by Kunii's group in Japan, Battelle-Columbus and FERCO in the United States, TNEE in France, AVSA in Belgium, etc., ... and Corella and Herguido's gasifier, which was operated during the period of 1989-1991. A description of the gasifiers operated today in Europe (TU Wien and Gassing in Austria and ECN in The Netherlands), Japan (IHI Co., EBARA, AIST-Tsukuba), and the People's Republic of China (Dalian, Hangzhou, and Beijing) then is given. Their most-relevant operation data, and the results from these gasifiers (mainly, the gaseous hydrogen (H-2) and tar contents in the raw produced gas), are finally presented briefly.