The Vojvodina province is the most important agricultural area of the Republic of Serbia and is its largest soybean producer. Serbian low forbids the introduction of genetically modified organisms (GMO) into the environment and demands labeling of food containing more than 0.9% GMO. This aim of this study is to monitor the Roundup Ready (RR) soybean in fields and in food products using PCR and immunoassays. A duplex PCR reaction was performed to analyze the lectin gene and 35S promoter using DNA isolated from soybean leaf and seed sample. Specific detection of RR markers was performed using nested PCR and verified by immunoassay. RR soybeans were found in 68 fields in samples from 2003 and 28 fields in 2004. The presence of the RR soybean was confirmed in 44 seed samples out of 7142 samples examined in 2006 and in 108 out of 7171 samples examined in 2007. The data presented here are the first to demonstrate the presence of RR soybean in the Serbia fields.