Conductive (150 μω cm), adherent films of zirconium and hafnium borides have been deposited on various substrates by the low-temperature (100-270 °C) thermal decomposition of Zr[BH4]4 and Hf[BH4]4. Auger electron spectroscopy of these films shows that their composition is ZrB2 and HfB2. The film surfaces are oxidized and slightly carbon contaminated. However, the bulk contains less than 1 at. % C or O. This synthesis is by far the lowest temperature preparation of these materials (plasma-enhanced chemical vapor deposition of TiB2 requires 480-600 °C) and holds great promise for the use of these materials in electronics applications.