Technical Abstract: Soybean, Glycine max (L) Merr., is grown on 1,420,000 ha in North Dakota and is the most important oilseed crop in the state. Viruses in soybean have not previously been reported from North Dakota (1). In July and August of 2007, 64 soybean fields in Cass, Richland and Sargent counties in southeastern North Dakota were surveyed for Soybean mosaic virus (SMV). These counties have a high concentration of soybean hectares, a long history of soybean production and soybean aphid infestations have been observed. Fields were sampled on a grid pattern across the area with at least 5 miles between fields. A transect of about 60 m through each field was made and 20 leaves were collected at random. Sap was extracted in phosphate buffer and stored at -80° C until tested first with double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) using positive controls and reagents and protocol from Agdia (Elkhart, IN). Using DAS-ELISA, SMV was detected in 19 of the 64 soybean fields sampled. To confirm the presence of SMV, twelve samples that were positive for SMV by DAS-ELISA also were tested using reverse transcription-polymerase chain reaction (RT-PCR). RNA was extracted from sap using Qiagen RNeasy Plant Mini Kit (Germantown, MD), reverse transcribed, and amplified with SuperScrip III Platinum SYBR Green One-Step qRT-PCR kit (Invitrogen, Carlsbad, CA), and SMV-specific primers (5'-TTCAGCACAATGGGTGAGGATG-3' and 5'-AATTCTGTGTGGCTTGATGTTGC-3'). Eight of the 12 ELISA-positive samples were positive for SMV by RT-PCR, confirming the presence of SMV in the samples. To our knowledge this is the first report of SMV infecting soybean in North Dakota.