La dilatación aneurismática, 1,5 veces el diámetro del vaso mayor normal que compromete un segmento de arteria coronaria, es una patología de rara presentación (incidencia 1,5% a 5%). Su etiología es arteriosclerótica y su principal importancia clínica es la posibilidad de producir infartos por trombosis o espasmo y ruptura. No se conoce su evolución y pronóstico y en la literatura no hay material suficiente para realizar recomendaciones sobre el tratamiento. Se reporta un caso de aneurisma del tronco principal y se revisa la literatura con el objetivo de actualizar la información al respecto.Coronary artery aneurysm is defined as the dilation of a segment of the coronary artery that reaches 1.5 times its normal size. It is an infrequent pathology with an incidence varying between 1.5% and 5%. Its main cause is atherosclerosis and from a clinical point of view its importance resides in the possibility of producing infarcts through thrombosis or spasm, and in its rupture. The natural history and prognosis remain obscure and there is not enough evidence respect to its evolution and prognosis as to give the right guidelines for its treatment. We report the case of a patient with left main coronary artery aneurysm and make an update literature review on this subject.