Turnip mosaic Potyvirus (TuMV) and Ribgrass mosaic Tobamovirus (RMV) are major viruses infecting crucifer crops in Korea. RMV-FG22 was isolated from oriental cabbage. TuMV isolates were TuMV-CA7 from oriental cabbage, TuMV-TU and TuMV-TU2 from turnip, TuMVRA from rape, TuMV-ST from stock, and TuMV-R9 from radish. The six isolates of TuMV were classified by symptom expression in inbred lines of crucifers. TuMVCA7 and TuMV-TU isolates infected mostly oriental cabbages; TuMV-ST, TuMV-TU2, and TuMV-R9 infected radishes; and TuMV-RA infected both oriental cabbages and radishes. Crops used in six combinations of mixed infections were ``Tambok`` cultivar resistant to TuMV, ``SSD63`` susceptible inbred line of oriental cabbage, pure line of leaf mustard, and ``Daeburyungyeorum`` cultivar of radish. External symptoms in ``Tambok`` and radish by each of the six single infections of TuMV showed similar results by bioassay. Synergistic response of necrotic death occurred within 1 week after inoculation in all combinations mixed with TuMV and RMV-FG22 on leaf mustard. In oriental cabbage ``SSD63``, synergism of necrosis occurred in four TuMV isolates, but not in TuMV-ST and TuMV-R9. In oriental cabbage ``Tambok``, synergism was expressed only in two combinations of RMV-FG22+TuMV-CA7 and RMV-FG22+TuMV-TU, but other combinations had the same symptoms produced by RMV-FG22. In radish ``Daeburyungyeorum``, only mild mosaic symptoms were induced by combinations of RMV-FG22+TuMVCA7, RMV-FG22+TuMV-TU, RMV-FG22+TuMVRA, and RMV-FG22+TuMV-R9. Mosaic and severe mosaic were induced in combinations of RMV-FG22 +TuMV-TU2 and RMV-FG22+TuMV-ST, respectively.