We have fabricated nanoporous alumina surfaces by means of anodization in oxalic acid in different conditions and used them as the substrates for the growth of cells from a human osteoblast-like cell line. The rough nanoporous alumina substrates have been compared both with smooth standard Petri dishes used as the control and with commercial substrates of similar material. The viability of the cells has been assessed at different culture times of 4, 11, 18, and 25 days in vitro. It turned out that the porous side of the galvanostatically fabricated alumina performed similar to the control and better than the commercial porous alumina, whereas the potentiostatically fabricated porous alumina performed better than all the other substrates at all times, and in particular at the two shortest time periods of 4 and 11 days in vitro. The best performance of the substrates is associated with intermediate surface roughness and feature spacing.