The renal and respiratory systems regulate acid base homeostasis by modifying the bicarbonate buffer pair HCO3- and CO2; other buffer systems adjust to alterations in this pair. The pH change following addition of metabolic acid, or base, is modified initially by the body's buffers. Subsequent respiratory compensation, by retention or excretion of CO2, modifies further this change before renal corrective responses finally occur. A primary respiratory acid base change is modified initially by cellular buffers, with renal compensatory mechanisms adjusting slowly to this change. However correction of the respiratory pH disorder only occurs with correction of the primary disease process. The body's capacity, therefore, to adjust to a metabolic acid base defect, appears greater than that observed with a primary respiratory pH abnormality. Treatment in all acid base disorders focuses initially upon the primary diseases process; thereafter therapeutic manipulation of the HCO3 -, CO2 buffer pair, to aid the body's compensatory processes, can be considered.