Metabolic acidosis was induced in 18 piglets of Swedish native breed by prolonged iv infusion of lactic acid, which decreased both blood and muscle pH. A two- to three-fold increase in muscle lactate content was related to the decrease in muscle pH. Treatment of the induced metabolic acidosis with either sodium bicarbonate or a tris buffer mixture re-established normal or near-normal arterial pH, but PaCO2 remained elevated after sodium bicarbonate infusion. The pH in muscle and cerebrospinal fluid (CSF) normalized only in the group treated with the tris buffer mixture. Thus, the tris buffer mixture was more effective than traditional sodium bicarbonate in correcting the acid-base disturbance in the CSF and the muscle intracellular compartment.