Soybeans collected from different locations in Korea were planted for tests of seed transmission of soybean mosaic virus (SMV). The percentage of seed transmission ranged from 20.5 to 29.5% in 14 seedlots including soybean cultivar Namhe and 12 to 19% in other 44 seedlots. However, no seed transmission of SMV was observed in soybean cultivar Younkiyongho. SMV was detected from embryo and cotyledon of soybean seeds. The infection of SMV was highly detected from premature seeds than from fully mature seeds, and higher from seeds harvested from plants infected before June 20 than plants infected around July 20 and August 20. No significant relationship was observed between seed transmission of SMV and mottling of seeds. The incidence of soybean mosaic disease followed by one month after peak of aphid population. The number of aphids was less on leaves of soybeans with short and dense trichomes whereas it was higher on leaves of soybean with long and sparse trichomes. Generally, the number of aphids was decreased on leaves with long and dense trichomes as the growth progressed. Soybean cultivar Columbus and 14 cultivars were susceptible, Chief and 14 cultivars were moderate, but Jangbaek and 17 other cultivars were resistant to SMV when inoculated with one isolate of SMV.