The microscopic polyarteritis is a vasculitis related to necrotizing glomerolunephritis. It always damages at renal and systemic level (a third of the cases presented hemorrhage alveolar). We have showed a case that took place with hemoptysis and renal progressive insufficiency. Among the patient antecedents, we can find arterial hypertension hematuria, rhinitis, epistaxis and artromyalgias. Just before his admittance it showed edemas on lower limbs and eyelids, dysnea, severe hemoptysis, paresthesias and general malaise. The immunologic analysis: Acs. glomerular basal antimembrane: negative, ANCA positive with antimieloperoxidasa specificity. The renal biopsy: focal necrotizing glomerulonephritis with semilunar and negative immunofluorescent. The nasas biopsy: unspecified chronic rhinitis. From the clinic point of view, the patient seemed to have the Wegener granulomatosis apart from the fact that he had hemoptysis which is a rare sign in this cases. However, we could not find any granuloma anatomopatologically, which did not clarify this diagnosis. We diagnosed microscopis Poliarteritis, as a third of the cases presented intrapulmonary haemorrhage. Moreover the renal damage it is identical than in the in Wegener granulomatosis. On the top of that, often we can find p-ANCA, which confirms the diagnosis in 99% of cases. Despite our doubt according to the diagnosis the therapeutical treatment of both illnesses is nowadays identical. This means that we were able to begin a precocious treatment with plasmapheresis, metilprednisolona and ciclofosfamida. After a week treatment there was an evident improvement. Five moth later the illness relapsed.