[Adherence to drug treatment among registered users in the "HIPERDIA" Program in Teresina in the State of Piauí]. 
Arterial hypertension and diabetes mellitus are among the most chronic diseases prevalent in Brazil.  The study sought to evaluate the socioeconomic profile and the therapeutic adherence of users registered in the HIPERDIA Program in Teresina in the State of Piauí.  This research was conducted in the Primary Healthcare Units, where a questionnaire was given to four hundred people evaluating their adherence based on the Batalla and Morisky-Green tests.  The socioeconomic profile of interviewees was as follows: senior citizens, women, married with 1 to 4 years of study, pensioners and salaried employees.  Only 22.5% of hypertensive and 30.7% of diabetic interviewees were considered adherents according to Batalla, and among all of them only 26.75% were adherents according to Morisky-Green.  There was no association between sociodemographic and clinical variables and adherence according to Morisky-Green, however there was an association with the type of morbidity presented.  In light of these results, health education is the main strategy to improve adherence of users as well as the participation of professionals in the Family Healthcare Team, including the pharmacist, the nutritionist and the physical trainer.