Tonsillectomy seems to be a logical step in IgA nephropathy owing to the frequent tonsillitis before the beginning and the acute exacerbations of the disease. The usefulness of tonsillectomy is questionable because there are only few and short-term follow-up data after it. We followed up 35 kidney biopsy proven IgA nephropathy patients (25 men and 10 women) for an average of 12.2 yrs (range 7-32) after tonsillectomy. The values of endogenous creatinine clearance, serum creatinine, hematuria and proteinuria were compared at regular intervals during a follow-up with those obtained before tonsillectomy. We considered more than 12,000 data using 2 tailed t test. We found that proteinuria started to decrease significantly already 6 months after tonsillectomy (1.40 +/- 0.27 g/day before tonsillectomy vs 0.92 +/- 0.25 g/day after it, p < 0.05) and was significantly lower under follow-up. The tendency in microhematuria was similar (70.5 +/- 35.0 million RBC/12 hours before and 14.0 +/- 6.5 million RBC/12 hours 6 months after tonsillectomy, p < 0.0001). Furthermore, tonsillectomy stopped gross hematuria appearing in the acute exacerbation of the disease in more than two-thirds of patients. Creatinine clearance did not change in the first 2 years after tonsillectomy, however, from 2.5 years after it is significant slow and continual decrease started (117.0 +/- 9.8 ml/min before and 106.2 +/- 10.8 mil/min 2.5 yrs after tonsillectomy, p < 0.05). End-stage renal failure was detected only in 4 patients out of 35 after 10 years after tonsillectomy, in our non-tonsillectomised control group in 8 patients out of 40.