Relapse cases are rare in patients treated regularly with multidrugtherapy (MDT) schemes recommended by World Health Organization. Leprosy relapse related to drug resistance have been reported since the 60s, especially related to prolonged use of Dapsone. Drug resistance can be studied by mouse foot pad inoculation by using the Shepard Tecnique and most recently by Polymerase Chain Reaction (PCR). Few researches have detected cases of drug resistance, some even with multiple drug resistance, which can jeopardize the efficacy of MDT in the future. A relapse of Hansen's disease should be considered when the patient, after having completed the adequate treatment and being discharged as cured, presents again with signs and symptoms of illness activity. Leprosy relapse cases are rare in patients treated adequately with MDT and usually occur 5 or more years after released from treatment. The clinical manifestations, that usually occur may be cutaneous (new lesions, increase of preexisting lesions, erythema and infiltration, non-traumatic lesion ulceration) and/or neural (thickening and/or hyperesthesia of nerves and trunks previously normal; paresis or paralysis of muscles that were not affected before, new anesthetic areas or exacerbation of sensibility alteration in previously affected areas).