Opioid addiction is a chronic disease with a relapsing trend including unpredictably-long periods of remission and complete will-being, but at high risk of relapse.Selective antagonists of mu, kappa and lambda receptors of the opioid system are among the commonest therapeutic means to prevent relapses and include naltrexone.Therefore, the aim of this report was to evaluate different administration regimens for naltrexone in a 12-mo follow-up to keep a drug-free condition with respect to the different therapeutic requirements and compliance of the treated patients.Seventy-two patients (64 males and 8 females) were enrolled.Patients were divided in three groups of 24.In the 1st group a member of the family was in charge for daily administration of the antagonist (50 mg tabs).Due to personal reasons, no psychol. support could be given to patients in this group; these patients only underwent a weekly test to rule out narcotics intake.The 2nd group received a daily administration (50 mg tabs) by a member of their families, psychol. support and toxicol. tests twice a week.The 3rd group received a daily administration (50 mg tabs) by a member of their families, psychol. support, toxicol. tests twice a week and antagonist administration by healthcare professionals of the Therapeutic Services every 10 days.The following results were obtained at the end of the study: in the first group, 9 patients withdrew from treatment within the first three months, 7 withdrew after 6 to 12 mo, resuming heroin use, 8 of the treated patients are currently drug-free.In the second group, 6 patients withdrew from treatment within the first three months and 6 of them after 6 to 12 mo resuming their opioid habits; 12 patients are drug-free.Finally, follow-up of the third group showed 2 and 3 patients to have withdrawn from the trial within the first three months and after 6 to 12 mo, resp., resuming their heroin habits; 19 patients of this group are currently still drug-free.The results obtained in this trial confirm that treatment with an opioid antagonist allowed us to keep a large number of patients drug-free.