To the Editor: In an article in the December 6 issue, Dr. J. H. Brezin and his co-workers stressed the renal toxicity of nonsteroidal anti-inflammatory agents. This kind of drug, particularly indomethacin, has been used in nephrotic syndrome of various origins. It seems able to reduce proteinuria, but the long-term effects of the drug in primary renal diseases are not known.We observed irreversible renal failure in children with steroid-resistant nephrosis treated with indomethacin. Our study was designed as a controlled trial comparing the effects of chlorambucil (0.2 mg per kilogram of body weight for six months) and of indomethacin . . .