Experiments were conducted in situ and in vitro in the ceca to measure ammonia production from uric acid, urea, and amino acids and its absorption. When uric acid was injected into a cecal sac containing mixed cecal microfloras, 77% disappeared within 1 hour, with a concomitant increase in ammonia concentration. When [15N]uric acid was added to the ceca in situ, 28% was converted to ammonia after 30 minutes. About 92% of the ammonia introduced into a cecal sac disappeared from the lumen fluid within 30 minutes. About 43% of each of urea nitrogen and glutamine-amide nitrogen was converted to ammonia-nitrogen, and 25% of uric acid-nitrogen and epsilon nitrogen of the arginine was found in ammonia. The conversion of aminonitrogen of glutamic acid and glycine to ammonia amounted to 19-20%, whereas that of alpha-alanine totaled 11%. It is concluded that dietary and urinary nitrogenous compounds that find their way into the ceca are useful nitrogen sources for ammonia production by microflora in the ceca of the chicken, and that ammonia is absorbed rapidly from the ceca.