Sixteen spring wheat cultivars were screened for resistance to maize streak virus (MSV) in the eastern Transvaal where the disease often attains epidemic proportions in wheat and maize. In this area four cultivars were resistant, two were susceptible and ten showed intermediate reactions to the virus. Tests on F1plants from crosses between resistant and susceptible cultivars showed that resistance is partially dominant. The observed variation in reaction of cultivars to MSV in different geographical areas is attributed to varying numbers of effective vectors as well as to the occurrence of different strains of the virus.