Catecholamine release is known to be regulated by feedforward and feedback mechanisms. Norepinephrine (NE) and epinephrine (E) concentrations rise in response to stresses, such as exercise, that challenge blood glucose homeostasis. PURPOSE: To assess the hypothesis that the lactate anion is involved in feedback control of catecholamine concentration. METHODS: Six healthy active men (26 ± 2 yr, 82 ± 2 kg, 50.7 ± 2.1 ml^.kg^{- 1.}min^-1 VO_2peak) were studied on 5 occasions after an overnight fast. Plasma concentrations of NE and E were determined during 90 min of rest and 90 min of exercise at 55% of VO_2peak twice with exogenous lactate infusion (lactate clamp, LC) and twice without lactate clamp (CON). The blood lactate profile (~4mM) of a preliminary trial at 65% VO_2peak (65%) was matched during the subsequent LC trials. RESULTS: In resting men, plasma NE concentration was not different between trials, but during exercise all conditions were different with 65% > CON > LC (65%: 2115 ± 166 pg/ml, CON: 1573 ± 153 pg/ml, LC: 930 ± 174 pg/ml, P<0.05). Plasma E concentrations at rest were different between conditions with LC lower than 65% and CON (65%: 68 ± 9 pg/ml, CON: 59 ± 7 pg/ml, LC: 38 ± 10 pg/ml, P<0.05). During exercise E concentration showed the same trend (65%: 262 ± 37 pg/ml, CON: 190 ± 34 pg/ml, LC: 113.2 ± 23 pg/ml, P<0.05). CONCLUSIONS: Lactate attenuates catecholamine response during moderate intensity exercise, likely by feedback inhibition.