Introduction Reusability is a key issue on e-learning contents and systems. Providing reusable learning objects can facilitate its further development and adaptation, augment learning object development productivity, reduce development costs and improve quality. Although reusability is an intrinsic characteristic of the learning object that can provide a priori a measure of its quality, reusing learning objects is an empiric and observable fact that can be compared with such measures by means of a posteriori data compiled from their actual use. Nevertheless, studies on reusability indicators and design criteria that guarantee reusability are scarce [1].