Primary IgA nephropathy (IgAN) is the most frequent type of primary glomerulonephritis worldwide. The characteristic presentation is gross hematuria at the time of an infectious episode. A renal biopsy still is mandatory for the diagnosis. The natural history of the disease is characterized by clinical and pathologic progression over time, which can vary from a few years to more than 50 years. It is possible to make a broad prediction at the time of diagnosis of the long-term (20 years) risk of progressive chronic kidney disease, and then to end-stage renal disease requiring renal replacement therapy (20-year cumulative end-stage renal disease risk range, 14%-39%). The 3 major independent risk factors are arterial hypertension, proteinuria more than 1 g/d, and severe renal histopathologic lesions including hyalinosis, crescents, or defined by histopathologic scoring systems. When any clinical risk factors are present, patients should be targeted closely by appropriate treatments in the following order: (1) precise control of hypertension, (2) control of proteinuria when persisting for greater than 1 g/d, and (3) evidence-based treatment where available for severe lesions. This is a symptomatic treatment strategy because pathogenesis and etiology still remain unclear.