PURPOSE reporting three rare cases of Marcus Gunn Syndrome and analyzing the clinical features of this entity. METHODS Case reports of three patients with a Marcus Gunn Syndrome, treated at the Ophthalmology B CHU service Rabat - Morocco. RESULTS Our patients are two boys aged 1 and 2 years old, and a 31 year old woman with a Marcus Gunn Syndrome. As special features, in the boys' cases this syndrome is bilateral, as for the other case it is associated with congenital fibrosis clinically predominant of the Ipsilateral inferior rectus muscle in an adult. Surgical treatment was not offered for children because of their young age. The adult patient has benefited from a recession of the inferior rectus muscle and a pleating in the superior rectus muscle. The forced duction test objectified a fibrosis of the inferior rectus muscle. Surgical correction of Ptosis and Synkinesis has not been indicated in this patient, given the residual oculomotor disorder and the risk of exposure keratitis. CONCLUSION Marcus Gunn Syndrome is exceptional in adults. This can be explained by the tendency of the lid retraction to fade with age. Bilateral involvement in Marcus Gunn Syndrome is rare. Its association with congenital fibrosis of extraocular muscles has allowed a better etiopathogenic approach highlighting a supra nuclear origin of this Syndrome.