A new disease, named citrus sudden death, affecting trees of sweet orange [Citrus sinensis (L.) Osb.] grafted on the ‘Rangpur’ lime (C. limonia Osb.) rootstock was first detected in 1999 in the southwestern part of Minas Gerais and northern part of São Paulo states. Initially, affected trees present pale green leaves, followed by pronounced leaf drop, twig dieback, and occasional growth of a few small sized suckers on the scion. Finally, trees quickly loose all their leaves and die. Sometimes fruits remain attached to the twigs of dead trees. Cambial yellowing in the rootstock can be observed being this the main diagnostic symptom of the disease. There is no graft incompatibility. Symptoms have already being found in 2 yr and 2-mo old plants; however, they are more frequent in trees older than 6-yr, and more pronounced during the spring. The root system shows accentuated loss of feeder roots and root rot. The spatial evolution suggests a viral cause with airborne transmission. Experiments aiming to both determine the nature of the disease through biological and molecular tests and to find control methods are being carried out. Index terms: sweet oranges, ‘Rangpur’ lime, cambial yellowing, lack of feeder roots.