Callus cultures have been developed from leaf nodes of wheat ( Triticum durum, Desf. Ramsey) infected with wheat striate mosaic virus (WSMV). This callus tissue consisted of discrete clumps of cells, with the youngest cells in the center and the oldest cells on the outside of the clump. Electron microscopic studies revealed numerous plasmodesmatal connections in young callus tissue; in addition the cytoplasm became less contrasted and large central vacuoles developed as the cells aged. WSMV particle were observed in abundance within both the nuclear envelope and the cytoplasm of the virus-infected callus cells. However, except for the presence of the virus, there did not appear to be any difference in the ultrastructure of WSMV-infected and healthy callus cells.