A virus, inducing mosaic and malformation of carrot leaves (Daucus carota L.), was found in Piedade, SP. It was termed carrot mosaic virus (CMV), and is both mechanically and aphid transmitted. Morphologically it belongs to the potato virus Y group (15m¼ x 740m¼). Electron microscopic examination of thin sections of leaf tissues from carrot or coriander (Coriandrum sativum L.) infected with CMV demonstrated the presence of cytoplasmic inclusions, usually in the form of dense bands. They could reach sizes up to 0.2¼ x 4¼ and were detectable even under light microscopic examination. These bands, at higher magnification, showed to be built up of thin lamella (10-15m¼ thick), closely apposed. Occasionally individual or group of lamella appeared to loose from the bands, producing other type of profile, such as pin wheels and rings. CMV particles were sometimes observed in the vicinity of these inclusions, often laying parallel to their surface. These inclusions are identical to those observed in tissues infected with other components of the potato Y virus group, and their detection seems to corroborate the previous inclusion of CMV in this group, basead on particle morphology. Besides these cytoplasmic inclusions, some cells contained a large number of vesicles in the cytoplasm, apparently associated with Golgi complex activity.