Pure acute Pandysautonomia (PAP), first described in 1969 by Young, is a rare but well defined clinical entity, in which the isolate involvement of Autonomic Nervous System (ANS) gives rise to a characteristic clinical admixture of symptoms and signs all due to the alteration of parasympathetic and sympathetic control of neurovegetative functions. The most prominent clinical features are: 1) postural hypotension without changes in heart rate leading to orthostatic syncopal or near-syncopal episodes, 2) abnormalities of intestinal tract and urinary bladder motility, leading to constipation alternating with diarrhea and urinary retention, 3) loss of sweating, 4) ocular abnormalities. We report a case of a 17 year old man with PAP, in whom almost complete resolution of clinical symptoms and signs of ANS involvement was observed within 9 months from the onset of illness. In our case, besides an accurate clinical and laboratory follow-up, particular attention was paid to investigate the cardiac responses to autonomic reflex tests and pharmacological interventions (atropine and beta-blocking drugs administration) during the entire course of illness. During the acute phase, complete vagal and almost complete beta-sympathetic "denervation" of the heart leading to disabling postural hypotension, fixed resting tachycardia and total unresponsiveness to Valsalva manoeuvre, were observed. PAP is a rare condition which must be known from cardiologists for a more complete knowledge of the etiology and pathophysiological mechanisms of postural syncopal attacks and must be distinguished from the less favourable progressive autonomic failure of the Shy-Drager syndrome.