A review is given of anodic alumina film formation on aluminium, with barrier and porous films developed by anodic polarization in an appropriate electrolyte. Initial consideration of barrier-type films, using marker and tracers, allows definition of the locations of film growth and consideration of the transport processes under the high electric field. From this base, the effects of altering him growth conditions, generally using acid electrolytes, to generate porous anodic films are considered, with be resultant films of defined morphology thickening as a result of the dynamic equilibrium between film growth at the metal-film interface and field assisted dissolution at the pore base-electrolyte interface. Means for characterising the developed films are presented as well as applications of the porous, amorphous film material.