IgA nephropathy (IgAN) is the most common chronic kidney disease in Japan, but the optimum treatment remains controversial. Our objective was to evaluate the effect of tonsillectomy and corticosteroid therapy combined with methylprednisone pulse therapy in patients at our hospital who had IgAN. Tonsillectomy plus pulse therapy was evaluated in 72 patients (33 men and 39 women) with a diagnosis of IgAN based on renal biopsy who were followed up for more than 1 year. The mean age of the patients was 35.2 +/- 10.9 years (range: 20-58 years) and the mean observation period after tonsillectomy was 20.3 +/- 9.7 months (range: 12-36 months). After tonsillectomy, steroid pulse therapy was administered (methylprednisolone at 500 mg daily for 3 days) 1-3 times and was followed by oral prednisolone from an initial dose of 30 mg on alternate days that was tapered gradually over one year. At 2 years after tonsillectomy, serum creatinine was unchanged or improved in the majority of patients, but worsened in 5 patients. Hematuria (erythrocytes/HPF) improved from Grade 3.76 (11-30/HPF) to Grade 1.94 (1-5/HPF) on average (we defined the grade of hematuria). None of the patients experienced exacerbation of hematuria. Proteinuria decreased from 1.32 g/day to 0.86 g/day (65% of the pretreatment value), and only 4 patients showed an increase of proteinuria. Mean protein loss decreased to less than 0.5 g/day in patients with creatinine clearance > or =90 ml/min and/or patients with initial protein excretion < or =1.0 g/day.