Based on the national implementation of a health information system (HIS) involving 156 Centers for Testing and Counseling on STD/AIDS (CTC) , we propose: a) a theoretical model concerning factors that might make the stablishment of a new information technology (IT) viable (or not) for the CTC; b) to assess the performance of the model proposed. The data collecting processes and those for the HIS implementation contexts are the same. Three of the technologies for operating the new HIS implementation used by the federal government stand out: sensitivity meetings, capability workshops and technical supervision visits. Structural questionaries were applied to the capability workshops. The supervision visits to the 13 CTC permitted observation on the practices as well as interviews with managers and health workers. Using “Mario Testa’s coherence principle” as reference, we analised the adequacy involving the Method (“how to do it”) used by the federal government, the Aims of the implementation (“for wh at and to whom”) and the Organization “where the new IT is applied”. On making use of the model proposed, the implementation of the new HIS happened by adherence. Also, computers have not been provided by the Ministry of Health (MH). The management of the “uncertainty” has been the main strategy on leading the implementation of the new HIS, putting emphasis on the “communicative action” concerning the practices agents. The symbolical cement of this process has been the mission to improve counselling practices and the managing procedures from the introduction of the new HIS. All the rest is to be incomplete and everbuilding social construction. The managers’ and workers’ support depend basically on the agents’ sensitivity to figure out: a) the new system makes their job easier; b) makes it more valuable and of more significance; c) increases their control power over the organization; d) there is coherence between the objectives expressed and the methods and techniques used for the implementation of t he system. Thus, it was necessary to handle the agents’ expectations all through the process. As final results, 112 CTC, 71.8% of those being trained, implemented the new HIS. As to the reproduction of this theoretical model, it will certainly depend on its own possibility of application onto different contexts. After full studies implemented, this is when it is possible to compare variations in different contexts and its consequences so that we will be able to develop a steady theory to explain the phenomenon under investigation.