BH4, with isotopic substitution, has been prepared and trapped in solid H-2, D-2, HD by laser vaporization of boron and subsequent reaction with the matrix gas. The results confirm the C-2v structure of the molecule and generally support the results of Symons et al., on gamma-irradiated NaBH4. Differences from those results are discussed, and comparison is made with the CH4+ parameters of Knight et al. (C) 1997 American Institute of Physics.