The EtOH extract of Croton shiedeanus Schlecht, medicinal species used by the popular tradition in Colombia for hypertension, relaxes vascular rings of Wistar rat aorta stimulated with phenylephrine (10-6 M, alpha adrenergic receptor agonist), in a dose-depending manner, with an EC50 of 1.3 × 10-5 g/mL. This effect is superior to that exercised over rings stimulated with KCl (6,0 × 10-2 M, voltage-dependent calcium channel activator) and is reduced in vascular rings without endothelium. The vascular relaxation is reversed in the presence of methylene blue (1.0 × 10-4 M, guanylate cyclase inhibitor) and L-NAME (10-4 M, nitric oxide synthase inhibitor), and is not affected in presence of propranolol (10-6 M, beta receptor antagonist), atropine (30 × 10-5 M, muscarinic antagonist) and indomethacin (10-6 M, cyclooxygenase inhibitor). Additionally, the contractions induced by CaCl2 (10-5 – 10-2 M, calcium currents activator) are not affected in the presence of EtOH C. schiedeanus extract (5.0 × 10-5 g/mL). Serial dilutions of L-NAME and methylene blue (until 10-14 M) show that C. schiedeanus recovers almost entirely the vasodilator effect in presence of L-NAME but not in presence of methylene blue (91 versus 68% of Emax, respectively). In addition, the relaxant potency and efficacy of C. schiedeanus is greater than its predominant active metabolite, ayanin (IC50: 1,3 vs. 4,9 × 10-5 g/mL, Emax: 100 vs. 67%). These findings suggest that C. schiedeanus exerts vasodilating effects, particularly related to the metabolic pathway of guanylate cyclase and gives support the traditional use of this species.