In this study we report on our investigation of the microstructure of nickel oxide films produced byse-beam evaporation, sol-gel deposition, and sputtering techniques. We give characteristic cyclicsvoltammetry, current-voltage relationships, and optical transmission data for films made by eachstechnique. Data is shown for electrodes, both uncycled and cycled, for 17-20 hrs. We found allssamples have at least one phase corresponding to cubic nickel oxide (NaC1 structure). Othersphases, such as nickel hydroxide, may exist but are not immediately identifiable. The structure ofsthe films ranges from fine polycrystalline to amorphous and varies over the surface of the sample.sFilms that were cycled for 17-20 hours all tended to have improved transmittance, as high as as20% change. The highest transmission range from bleached to colored was for the evaporatedsfilms, which showed delta T=60%. The sol-gel films showed a large residual coloration in thesbleached state after cycling (about a 40% decline was noted). Overall, after cycling the filmssappeared to be slightly more crystalline. In all films, after cycling there were increases in thescoloration and bleaching current. Also, peak shifts were noted after cycling; the coloration peakstended to shift to higher and the bleaching peak shifted to lower potentials. The overall colorationsefficiency (550 nm) for these films ranged from 26-36 cm2/C.