Nanostructured thin films of amorphous YBa2Cu3Ox were prepared using pulsed-laser glancing-angle deposition. Ambient oxygen pressure and laser fluence have a strong effect on the microstructure of the films. The films exhibit a structural evolution from isolated directional nanorods, through a. network of vertical nanocolumns, to nanoparticles fractal with increasing ambient oxygen pressures from below 1 to above 180 mtorr. The shadowing effect, surface diffusion,. and flux scattering by ambient gas play main roles in determining the structural evolution. 2006 American Vacuum Society.