The purpose of the current study was to investigate the role of in vivo beta-adrenergic stimulation on sweat production during exercise. To do this, atropine was used to block the cholinergic component of sweating, thus isolating any potential beta-adrenergic response during exercise. The subjects for this study were 11 healthy volunteers. Atropine (1% solution) and aminophylline (1% solution) were administered to a 5 cm(2) area of the flexor surface of one forearm via iontophoresis. The opposing arm underwent iontophoresis with a saline solution. Each subject then exercised at 75% of their age-predicted maximum heart rate. During exercise, mean+/-SD sweat rate in the control forearm was 0.63+/-0.50mg/cm(2)/min. There was no measurable sweat production in the arm pre-treated with atropine and aminophylline. Following exercise, iontophoresis of pilocarpine verified complete cholinergic blockade in the treated forearm. The results of the current study suggest that in vivo beta-adrenergic stimulation alone is not sufficient to elicit sweating in exercising humans. Such data supports previous studies that have suggested that the role of beta-adrenergic stimulation in vivo is to potentiate cholinergic sweating.