We present the results of detailed electrical measurements on diamond films grown by hot-filament chemical-vapor deposition. Two different mixtures of reaction species, hydrogen/methane and hydrogen/acetone, were utilized to grow diamond films. The latter is useful for introducing dopants during growth in a relatively safe manner. For the diamond films grown using hydrogen and methane, a high-temperature anneal increased the resistivity of the films by seven orders of magnitude to about 1012 Ω cm while the I-V characteristics retained the same qualitative shape. Further annealing was found to change the I-V characteristics of the film itself, not the contacts. Spatial variation of the electrical characteristics is also reported. In addition, for the diamond films grown using the hydrogen and acetone, a variety of different results was obtained. Electrical measurements and Raman spectroscopy suggest that some areas of these films were high-resistivity diamond while other areas may contain nondiamond carbon at grain boundaries.