Microsomal omega-3 fatty acid desaturase is an essential enzyme in the production of the n-3 polyunsaturated fatty acid alpha-linolenic acid during the seed developing stage. We have constructed a chimeric gene consisting of a maize Ubi1-P-int and a soybean GmFAD3 cDNA, which was introduced into rice plants by Agrobacterium-mediated transformation. Ten transformants containing the chimeric gene were established and expression subsequently confirmed by Northern blotting. Furthermore, alpha-linolenic acid content of the T(1) seeds increased dramatically up to tenfold that of the control, and this phenotype was also stably inherited in the T(2) and T(3) progenies. These results demonstrate that the alpha-linolenic acid content of rice seed oil can easily be altered using the combination of a high-activity promoter and a GmFAD3 gene.