We describe a method for quantitatively estimating 24 ninhydrin-reacting substances, including the commoner amino acids, in fecal dialysate prepared from ingested dialysis bags retrieved from fresh stool. It is accurate to 2 mumol of alpha-amino nitrogen per liter of fecal dialysate, and for most substances recovery of added standards is 100%. It involves dilution, ultrafiltration, and automated ion-exchange column chromatography of the dialysate. Some normal values are provided.