It is in the United Kingdom where medical prescription of opiates has been more widely used. Although these practice had been increasing until the sixties, several factors caused a decreased since then, so that it is currently 1.6% of all maintenance programmes, becoming methadone prescription more important. Mainly through studies conducted in Switzerland, the debate over the appropriateness of this practice. In such studies, it appears that heroin prescription supports important improvements in the patients outcome, as it is associated with better retention rates, a reduction in abuse of illicit substances, and improvements in patients health and social aspects. However, methodological limitations of these studies and ambiguous results of studies carried out in other countries, make it difficult to determine the effectiveness or efficacy of this pharmacotherapy, so that more studies are needed to scientifically justify this practice.