The authors report the case of a neonate who died early of refractory heart failure and presented with all the characteristics of Marfan's syndrome in its early form with articular retractions. There was clinical evidence of mitral, tricuspid and major aortic regurgitation. Two-dimensional and doppler echocardiography confirmed the prolapse of highly dystrophic valves and the quadrivalvar regurgitation. Typical lesions of the connective-elastic tissue were found at autopsy. The occurrence of malignant Marfan's syndrome in neonates seems to be exceptional; the syndrome may take the rare "en contractures" form. Death is not always ascribable to the cardiac pathology, this pathology being often less generalized than in our case which seems to be the first one where such diffuse and massive valval lesions have been observed. This particular form was comparable to the "congenital polyvalvular disease" described by Bahrati and Lev, except that the skeletal and visceral abnormalities of Marfan's syndrome are absent in that disease.