Allergenicitv of genetically-modified (GM) soybean was evaluated in male Sprague Dawley rats. To confirm the GM in this study, the polymerase chain reaction (PCR) was performed using the chromosomal DNA of soybeans. The PCR result provided the clear discrimination of genetically-modified (GM) soybeans. To evaluate the allergenicity of GM soybean and non-GM control the soybean homogenate was inoculated subcutaneously 3 times in 3 weeks. The doses of soybean were 0, 2 and 20mg/kg of  protein. A week after the last inoculation, antisera were recovered from individual animals. When the sera were injected intradermally on the clipped back of unsensitized rats with at various dilutions, followed by a challenge with 20mg/kg of soybean homogenate containing 1% Evans blue, no sign of passive cutaneous anaphylactic reaction was detected. In addition, when the sera were treated in cultures of peritoneal mast cells, the increase of histamine released by GM soybean anti-sera was not observed when compared to that by non-GM soybean anti-sera. The present results indicate that the GM soybean might not act as a strong allergen in male Sprague Dawley rats.