The main objective of HAART is to achieve a complete suppression of the viral replication for long time. However, when the therapeutic drug levels are low, HIV can replicate and it can develop resistances. This fact can be the reason of treatment failure, HIV transmission of resistant strains and therefore an inappropriate use of the economical resources. In order to get the adequate therapeutic drug levels it is necessary to have a good adherence to the treatment. We review the factors that influence the adherence, the evaluation methods and we recommend the possible intervention strategies which should be given by a multidisciplinary team, integrated by physicians, pharmacists, nurses, psychologists and other personal support. To start HAART is not an emergency. For this reason is very important to prepare to the patient and to identify the non-adherence factors in order to correct it. Once the HAART is indicated it is very important to offer information during the medical prescription and when the drugs are dispensed. During the therapy is necessary to follow actively all patients on HAART. In order to make therapeutical decisions we need to know the patient drug adherence rate. We recommend to use several methods to calculate the drug adherence rate, being the most commonly used the patient interview, the patient questionnaire, the refill count, the pharmacy visits rate together with the viral load evolution of the patient. In order to get all this information it is necessary to have a very good communication between all the people involved in HIV infected patients care. If non-adherence is detected it is necessary to start the intervention strategies to correct it and if they fail it might be necessary in some cases to stop HAART. The potential benefits of the adherence programs can justify the economical spend in human and hospital facilities resources.