Adult cats with normal renal function were fed a nutritionally balanced, vitamin A-replete, experimental dry diet with or without ammonium chloride (NH4Cl) for 6 mo to study the effects of chronic dietary acidification on acid-base parameters and the metabolism of selected minerals. Dietary balance studies were performed monthly. Blood and urine samples were collected monthly to evaluate acid-base parameters, plasma parathyroid hormone (PTH) and 1.25-dihydroxycholecalciferol levels. Ammonium chloride-treated cats had significantly lower blood and urinary pH, and lower blood bicarbonate concentrations. Treated cats also had higher blood ionized calcium concentrations, hypercalciuria and lower intestinal calcium absorption relative to baseline (prior to feeding the experimental diet) and to control cats. This resulted in the development of lower calcium balance in the first several months. PTH levels were unaffected by dietary acidification; however, 1.25-dihydroxycholecalciferol levels were significantly decreased in treated cats. Treated cats had negative potassium balance during 5 mo of dietary acidification. Magnesium, sodium, and phosphorus balances were lower, but positive, in treated cats compared to control cats. Cats consuming the NH4Cl-supplemented diet had increased chloride balance. Thus, chronic dietary acidification with 1.5% NH4Cl produced chronic metabolic acidosis and lower or negative, calcium and potassium balance.