This paper describes a modified synthesis of NaB<sub>3sub>H<sub>8sub> by the reduction of BH<sub>3sub>路THF with sodium dispersed on silica gel. Single crystals obtained from CH<sub>2sub>Cl<sub>2sub> show conclusively that the space group is Pmn2<sub>1sub>, in contrast to the Pmmn space group previously deduced from powder diffraction data.