The biological response to tonsillectomy was studied in 21 patients suffering from chronic tonsillitis with or without IgA nephropathy (IgAN). Serum and urinary interleukin-6 (IL-6) levels were measured before and after tonsillectomy. Serum IL-6 levels in case of IgAN peaked 3 h after tonsillectomy and more rapidly than control cases. No significant differences were observed between two cases through the time. Urinary IL-6 levels were significantly higher before and at 6 and 48 h after tonsillectomy in IgAN cases. Stimulation of tonsils caused serum IL-6 elevation and changes in urinary IL-6 levels in IgAN cases. Elevation of urinary IL-6 levels after tonsillectomy in patients with IgAN may reflect an increase in the production of IL-6 in the kidneys. Measurement of urinary IL-6 levels after tonsillectomy is useful to elucidate the efficacy of tonsillectomy in IgAN patients.