Two hundred and thirty one leaf samples of virus infected and mosaic and as well dwarf mosaic symptoms showing maize plants from various corn fields in Tehran province were collected during the growing season 2003. By performing serological tests of DAS-ELISA, DIBA and TPIA, using SCMV, MDMV, SrMV and JGMV antisera, only SCMV was detected in samples, with all samples reacting strongly to the SCMV antiserum. SCMV was determined as the main and prevalent potyvirus on maize in Tehran province. The virus was transmitted to sweet corn and sorghum plants using 0.1 M potassium phosphate buffer (pH 7) containing %2 Polyvinyl Pyrrolidon (PVP) for mechanical inoculation. For propagation and maintenance in greenhouse, the virus was propagated on sweet corn cv. Pars 403 and on grain sorghum cv. Kimia. The host range study with selected isolates of SCMV showed that the virus isolates were not transmitted by mechanical inoculation on Avena sativa, Panicum miliaceum, Setaria italica, Pennisetum americanum, Hordeum vulgare and Triticum aestivum. Purification of isolates was done using a minipurification method. UV absorbance spectra were obtained for purified viruses a ratio of A260/280=1.2 being calculated. Electron microscopic study using ISEM and decoration method with SCMV antiserum revealed filamentous flexuous particles of SCMV. In SDS-PAGE and western blotting tests on infected samples and purified isolates, the molecular weight of the virus coat protein was approximately 37-38 KDa. A difference among the CP of various SCMV isolates however, was not detected. Reverse Transcription-Polymerase Chain Reaction (RT-PCR) was done using SCMV F3 and SCMV R3 primers. where amplified fragments were found of approximately 900 bp in size as expected. The study indicated that SCMV is the prevalent potyvirus and the main causal agent of mosaic and dwarf mosaic on maize plants in the province.