Leprosy is an important public health problem in Brazil. However, this disease is still poorly diagnosed in its early stages, leading to permanent disability and disfigurement. We examined eight patients with clinical and histological diagnosis of multibacillary leprosy who were being treated for other diseases for about three years without clinical hypothesis of leprosy. These cases illustrate the importance of medical education and public information about leprosy’s signs and symptoms for prompt recognition and treatment, which are necessary to prevent permanent Leprosy is an important public health problem in endemic areas. In spite of governmental strategies for reducing the leprosy burden and leprosy control, with declining incidence since 1991 due to new strategies for dealing with this disease, including multidrug therapy with reduced duration of treatment and the adoption of new cure criteria, more than 250,000 new cases were registered in 2007, including about 40,000 in Brazil and 140,000 in India [1,2]. Leprosy is a chronic disease caused by an intracellular bacillus, Mycobacterium leprae, which multiplies very slowly. The incubation period of this disease is about five years. It is transmitted via secretion droplets, from the nose and mouth, during close and frequent contacts with untreated patients, which are the most important transmission foci. Clinically, leprosy mainly affects the nerves and skin. The commonest skin lesions are erythematous, hypopigmented and infiltrated plaques, which have reduced sensibility. Damage to the nerves explains the sensory loss; if untreated, there can be progressive and permanent disabilities. Other clinical aspects of leprosy are reactions, which may be defined as acute phases within the usual chronic evolution of the disease; sometimes these define the moment of diagnosis [3-5]. Diagnosis is clinical and treatment is made at public health facilities [2]. Eight patients were evaluated at the Clinical Dermatology Division of the Hospital das Clinicas da Universidade de Sao Paulo, where diagnosis of multibacillary leprosy was made clinically and histologically. All eight patients had been initially misdiagnosed. We present these cases, followed by a discussion regarding various aspects of Hansen disease and the importance of early diagnosis for preventing complications and transmission (Table 1). Discussion