We investigated the response of plasma and platelet:free catecholamine ([CA]) and sulphated catecholamine ([CA-S]) concentrations after an incremental treadmill test to exhaustion and during recovery. In triathletes (n = 9) plasma and platelet [CA] and [CA-S] were measured before, immediately after and 0.5 and 24 h after exercise. In long-distance runners (n = 9) and in controls (n = 10) plasma [CA] and [CA-S] were determined 2 h instead of 24 h after exercise. Platelet [CA] and [CA-S] remained unchanged throughout the study. Plasma [CA] increased after exercise in all groups (P < 0.05) and returned to pre-exercise values within 0.5 h of recovery. Plasma sulphoconjugated noradrenaline concentration ([NA-S]) was elevated after exercise in the triathletes, long-distance runners and in controls [9.96 (SEM 0.84) nmol.l-1, 11.8 (SEM 1.19) nmol.l-1, 9.53 (SEM 1.10) nmol.l-1, respectively; P < 0.05] compared with resting values [7.13 (SEM 1.04) nmol.l-1, 6.19 (SEM 0.56) nmol.l-1, 6.76 (SEM 0.67) nmol.l-1, respectively] and remained elevated after 0.5 h of recovery [9.94 (SEM 1.14) nmol.l-1, 10.96 (SEM 0.80) nmol.l-1, 8.95 (SEM 0.99) nmol.l-1, respectively; P < 0.05]. In the long-distance runners and controls plasma [NA-S] remained elevated during 2 h of recovery [9.96 (SEM 0.76) nmol.l-1, 9.03 (SEM 0.88) nmol.l-1, respectively]. These results would indicate that plasma [NA-S] increases after sympathetic nervous system activation by an exhausting incremental exercise test and remain elevated up to 2 h after exercise.