The programs of information retrieval for developing countries were analyzed, as well as the evaluation techniques applied to the usability, and those applied to the human-computer interaction, making emphasis on the empirical tests. A description was made of the work style of a full text information retrieval system distributed as a free software model, which has achieved an important diffusion level within the Peruvian academic community: the Cybertesis site. Subsequently, the usability problems of the search interface of the mentioned site reveals an excess of information in the presentation of the results, as well as omissions in the signs and labels used, and the absence of necessary search options as, for example, chronologic search. Finally, changes to the search interface of Cybertesis were recommended aimed at improving the effectiveness and efficiency of its information recovery system. © ECIMED.