The ventilatory response to acute (0–90 min) intravenous infusion of HCl was studied in awake, conscious rabbits with intact (CB +) and denervated (CB −) carotid bodies. The HCl dose was delivered such as to produce an increasing degree of acidosis over 90 min reaching blood pH values of 7.032–7.115 at 60–90 min and plasma [HCO 3 −] values of 8.5–10.6 mmol · L −1. CB − rabbits exhibit an increase in V T by 7 min and a decrease in Pa CO 2 by 15 min of infusion, changes that increased over 90 min. However, at all times the CB − response was significantly less than that in CB + rabbits. The relationships, percent decrease in Pa CO 2 vs Δ[H +] and percent increase V T vs Δ[H +], were well approximated by linear regression analysis in both CB + and CB − groups and the slope, as an index of the response sensitivity, was, in CB − rabbits, 0.33–0.37 of that in CB + rabbits. In the conscious, awake rabbit, peripheral chemoreceptors seem to account for up to 2/3 of the ventilatory response to metabolic acidosis.